Engineering Calculators Catalog
Browse our comprehensive suite of verified calculation engines and upcoming engineering workflows.
RO Recovery Calculator
RO recovery and permeate flow with full water and salt balance closure, concentrate concentration and salt loads.
Recovery (%) = (Permeate Flow / Feed Flow) × 100 RO Salt Rejection Calculator
Calculate membrane salt rejection percentage from feed and permeate TDS concentrations.
Rejection (%) = (1 - (Cp / Cf)) × 100 RO Salt Passage Calculator
Determine salt passage percentage through RO membranes and verify complementary rejection balance.
Passage (%) = (Cp / Cf) × 100 RO Permeate TDS Calculator
Project expected permeate total dissolved solids based on feed water salinity and rejection specs.
Cp = Cf × (1 - R / 100) RO Concentrate Flow Calculator
Brine/reject flow with water and salt balance closure, concentrate TDS, concentration factor and salt loads.
Qc = Qf - Qp = Qf × (1 - Y / 100) RO Osmotic Pressure Calculator
Estimate RO feed osmotic pressure using a simplified van’t Hoff model from TDS, temperature, and solute properties.
π = i × C × R × T RO Design Studio
Build a preliminary RO system design with feed inputs, staging, custom membrane data, sequential element estimates, balances, and warnings.
Q = A × S × (ΔP − Δπ) RO Mass Balance Calculator
Simplified TDS-based dissolved-solids balance for RO feed, permeate, and concentrate flow and quality checks.
Qf · Cf = Qp · Cp + Qc · Cc RO Scaling Risk & Pretreatment Analysis
Screen CaCO3 scaling risk in RO feed and concentrate using the Langelier Saturation Index (ASTM D3739) and the Stiff & Davis Stability Index (S&DSI) for high-TDS and seawater feeds.
LSI = pH − pHS · S&DSI = pH − pCa − pAlk − K RO Energy & Specific Power Calculator
Determine specific energy consumption (kWh/m³) based on operating pressure and pump efficiency, with optional energy recovery device savings.
SEC = Q_f × P / (36 × η_p × Q_p) · P_h = Q_f × P / 36 · P_erd = Q_b × P × η_erd RO Operating Cost (OPEX) & SEC Calculator
Estimate RO operating expenditure: pumping energy (specific energy consumption), chemical cleaning, antiscalant, and membrane replacement.
SEC = P_feed × Q_f/(η_pump·Q_p) · OPEX = Σ (energy + chemical + membrane + maintenance) RO Performance & Troubleshooting Analyzer
Compare a current measured RO run against its commissioning baseline: permeate flow normalized to 25 °C and baseline net driving pressure (ASTM D4516-style), salt passage, pressure drop, flux and specific flux — with directional, verify-in-the-field diagnostics.
Qn = Qm × (TCF_ref/TCF_use) × (NDP_ref/NDP_use) with TCF ≈ 1.03^(T−25) and NDP = P_feed,avg − P_perm − (π_feed − π_perm) Plant Mass Balance
Assemble the whole plant as an ordered chain of unit operations: raw intake to product and waste, stage-to-stage product flow, external make-up, derived concentrate TDS by salt conservation, and plant-wide water and salt balance checks.
product = feed × recovery/100 · waste = feed − product · Cw = (Qf·Cf − Qp·Cp)/Qw · intake + make-up = plant product + plant waste Water Analysis & Treatment Selection
Enter a feedwater analysis once: derive hardness, cation–anion charge balance, TDS by summation, ionic strength and saturation indices (LSI/RSI), then compare water-quality drivers against the treatment surfaces already built on the platform — a qualitative start, not a diagnosis.
hardness = 2.497·Ca + 4.118·Mg · balance% = 200·(Σmeq+ − Σmeq−)/(Σmeq+ + Σmeq−) · LSI/RSI via existing saturation engine Small & Modular Desalination Sizing
Size a small or modular desalination plant from a demand basis forward: community population to product flow, then feed and concentrate by the plant mass balance, then membrane area, vessels and staging. Composes engines that already exist; chooses no recovery, staging ratio, flux or package envelope.
No new formula: composes calculateWaterDemand → analyzePlantMassBalance → buildRoArray → buildModularPackageScope. Feed = product ÷ recovery; area = permeate ÷ design flux; vessels = area ÷ element area × elements per vessel. Filter Sizing Calculator
Size a conventional rapid-gravity multimedia filter from design flow, filtration rate, bed depth and media effective size: required filter area, design area after the engineer's safety factor, and media volume. The unit count needs a stated catalogue unit area, and no clean-water head loss is invented.
A = Q/v · design area = A × safety factor · units = ceil(design area / unit area) only when a catalogue unit area is supplied · media volume = design area × depth · no head loss is computed Cartridge Filter Sizing Calculator
Size cartridge and bag filter elements and housings from design flow, feed solids and the manufacturer's element flow rating: hourly solids load, element count and housing count. No element size is assumed and no differential pressure is invented.
solids load (g/h) = Q × feed solids · elements = ceil(Q / element flow rating) × safety factor · housings = ceil(elements / elements per housing) · no differential pressure is computed Disinfection CT Value Calculator
Compute the achieved CT value from residual disinfectant concentration and contact time, compare it against a required CT you state from your disinfection reference, and get the contact time the design needs to reach it.
CT = residual concentration × contact time · margin = (achieved − required) / required · contact time needed = required CT / residual · no required CT and no UV dose are built in Ultrafiltration (UF) Membrane Engineering
Size UF membrane area from permeate flow and design flux, compute transmembrane pressure from the feed/filtrate/concentrate pressures, and read normalised flux against the reference condition to expose fouling.
A = Qp/flux · TMP = Pf − (Pfilt + Pc)/2 · normalised flux against reference temperature Nanofiltration (NF) Membrane Engineering
Close the NF water and solute balance from a stated recovery and rejection to get permeate and concentrate flow and TDS, then size membrane area from the permeate flux.
Qp = Qf·Y · Qc = Qf − Qp · solute balance Qf·Cf = Qp·Cp + Qc·Cc · A = Qp/flux Ion Exchange (IX / IER) Bed Sizing
Size an ion exchange bed from service flow, resin volume and empty-bed contact time, and compute stoichiometric regenerant demand from the ionic loading.
V = Q·EBCT · service flow = Q/A · regenerant mass from stoichiometric ionic loading RO Concentration Factor & Salt Load Calculator
Compute RO water concentration factor (CF = 1/(1−Y)) and the salt load carried to concentrate for scaling and disposal analysis.
CF = 1 / (1 − Y) · Salt Load = Q_f × C_f × Y_loading RO Feed Pressure & Specific Energy Calculator
Estimate required RO feed pressure (permeate osmotic gap + net driving pressure) and specific energy consumption with optional energy recovery.
P_feed ≈ Δπ + (J × 100/B·SCP factor) + ΔP_friction RO Antiscalant & Chemical Dosing Calculator
Calculate antiscalant (or chemical) dosing rate and 100% active-equivalent flow from dose concentration and product strength.
Dose Flow = Q_feed × Dose_ppm / (C_prod × 100) (SG-adjusted) RO Membrane & Vessel Element Count Calculator
Calculate number of RO membrane elements and pressure vessels from permeate flow, design flux, and element area.
Elements = Q_p / (Flux × A_element) · Vessels = ⌈Elements / Elements per Vessel⌉ Desalination Plant Designer
Compose a whole desalination plant as an ordered chain of unit operations from raw intake to product and waste: design basis, stage recoveries and make-up, whole-plant water and salt balance checks, and concentrate TDS derived by salt conservation — every value labelled input, derived or missing.
plant recovery = final product / raw intake · stage product = feed × recovery/100 · concentrate TDS: Qw·Cw = Qf·Cf − Qp·Cp · membrane product TDS: Cp = Cf × (1 − R/100) Pump Power Calculator
Calculate hydraulic power, shaft power, and motor electrical power from head and flow rate.
HPump = ρ × g × Q × H / η Engineering Unit & Water Quality Converter
Convert flow rates and TDS concentration units (mg/L ↔ ppm) using the Site canonical unit engines (m³/day internal).
Canonical flow unit = m³/day · 1 mg/L ≈ 1 ppm (dilute aqueous) Pipe Flow & Friction Loss Calculator
Determine pipe velocity, friction head loss, and pressure drop via Darcy-Weisbach or Hazen-Williams.
v = Q / A · hf = 10.67 × L × Q^1.852 / (C^1.852 × D^4.871) Open Channel Flow (Manning′) Calculator
Compute open-channel velocity and discharge with Manning’s equation for trapezoidal, rectangular, and circular channels.
v = (1/n) × R^(2/3) × S^(1/2) · Q = v × A Pipe Flow Velocity & Sizing Calculator
Size a pipe to carry a target flow within a recommended velocity range, or check velocity for a given diameter.
D = √(4Q / (π·v)) · v = Q / A Reynolds Number & Flow Regime Calculator
Calculate Reynolds number for pipe flow and classify the flow regime (laminar / transitional / turbulent).
Re = ρ·v·D / μ Pipe Pressure Drop (Darcy–Weisbach) Calculator
Compute pipe head loss and pressure drop with the Darcy–Weisbach equation, solving the Colebrook friction factor.
hf = f × (L/D) × (v²/2g) · f via Colebrook-White Pump Head / Total Dynamic Head Calculator
Compose total dynamic head from static lift, friction losses, minor losses, and residual pressure.
TDH = H_stat + h_friction + h_minor + h_residual Pressure & Head Unit Converter
Convert pressure and head units: bar, kPa, MPa, psi, m H₂O, ft H₂O, and atmospheres.
1 bar = 100 kPa = 14.5038 psi = 10.197 m H₂O Volumetric → Mass Flow Converter
Convert volumetric flow to mass flow (and reverse) using fluid density, with common water/TDS basis.
ṁ = ρ × Q · Q = ṁ / ρ Water Quality Saturation Indices (LSI & RSI)
Evaluate calcium carbonate stability of a water with the Langelier Saturation Index (LSI) and Ryznar Stability Index (RSI) from pH, temperature, TDS, calcium, and alkalinity.
pH_s = 9.3 + A + B − C − D · LSI = pH − pH_s · RSI = 2·pH_s − pH Water Tank Storage Calculator
Size cylindrical and rectangular water storage tanks from dimensions or daily demand and residence time.
V = π/4 × D² × H · V = L × W × H Water Demand & Flow Requirement Calculator
Estimate community or facility water demand (domestic, commercial, fire) and the design flow requirement for supply and storage sizing.
Q_design = P · q · peakFactor · Q_avg = V_daily / 86400 Tank Fill Time & Filling Rate Calculator
Calculate the time to fill a storage tank from a known filling rate, or the filling rate required to meet a target time.
t = V / Q · Q = V / t Concrete Volume Calculator
Build a multi-item concrete quantity schedule for slabs, footings, beams, walls and columns, with category subtotals and an Excel export.
Per item: V = L x W x H (slab, beam, wall, curb) | L x W x D (footings) | A x H (columns) | (PI/4) D^2 x H (circular). Totals: net = SUM(items); supply = net + wastage%. Slab Concrete Volume Calculator
Calculate concrete volume for rectangular and L-shaped slabs with slab count and wastage margins.
V = A_plan × H · V_total = V × n · V_ready = V_total × (1 + wastage/100) · Bags = ceil(V_ready / 0.033) Footing & Foundation Volume Calculator
Calculate concrete required for spread (pad) footings and strip footings, per-footing and total volumes with ready-mix allowance.
V = L × W × D × n · V_ready = V_total × (1 + wastage/100) Column Concrete Volume Calculator
Accurate concrete requirements for round, square, and rectangular structural columns.
V = A × H × n · A = (π/4)d² round, b×b square, w×d rectangular Concrete Mix Design Calculator
Compute per-batch and per-cubic-meter quantities of cement, sand, aggregate, and water from a mix ratio.
V_dry = V × 1.54 · M_mat = V_dry × (ratio / Σ ratios) · Water = w/c × cement mass Rebar Weight Calculator
Compute theoretical rebar steel weight per meter and total tonnage from bar diameter and lengths.
W = d² / 162 (kg/m, d in mm) Rebar Quantity Takeoff Calculator
Estimate number of reinforcement bars required for slabs and walls based on spacing and cover.
Bars = ⌊(L - 2c) / s⌋ + 1 Masonry & Block Quantity Calculator
Estimate block quantities, mortar volume, and wall material takeoff from wall geometry and joint thickness.
N = ceil(L/courseW) × ceil(H/courseH) · Mortar = V_bed + V_perp Steel Weight Calculator
Compute structural steel and reinforcement weight for plates, bars, pipes, and standard sections using steel density.
W = V × ρ_steel (ρ ≈ 7,850 kg/m³) Construction Material Quantity Takeoff Calculator
Quantity takeoff for bulk construction materials with wastage: aggregate, sand, cement, and general volume-mass conversions.
Q = V × (1 + wastage/100) · m = Q × ρ Construction Cost Escalation & Scenario Calculator
Escalate a base construction cost to a target date with a user-supplied annual rate and compare alternative escalation scenarios.
C(t) = C₀ × (1 + r/100)^n · n = days ÷ 365.25 Embodied Carbon Screening & Comparison Calculator
Compare two design options on screened embodied carbon using user-supplied emission factors, with breakdown and per-m² intensity.
kgCO₂e = Σ (material quantity × user factor) · intensity = kgCO₂e / area Stormwater Runoff (Rational Method) Calculator
Estimate peak stormwater runoff with the Rational Method (Q = C·i·A) for drainage design and storm sewer sizing.
Q = 2.78 × C × i × A (L/s, A in ha, i in mm/h) Trench Excavation & Bedding Calculator
Calculate trench excavation volume, pipe displacement, bedding material quantity, and backfill volumes.
V_trench = A × L · Backfill = V_trench − V_pipe − V_bedding Earthwork Cut and Fill Calculator
Estimate site earth movement balance and bulk haulage volumes with swell and shrinkage factors.
Net = ΣCut − ΣFill (bank m³) · Export = Net × (1 + swell/100) · Import = −Net × (1 + shrink/100) MEP Electrical Load & Distribution Calculator
Screening-level electrical load and distribution takeoff: connected load, max demand, main cable length, distribution boards, MCBs.
Connected Load = Area × W/m² · Max Demand = Connected × Diversity · DBs = 2 × Floors · MCBs = 3 × Units MEP Plumbing & Water Supply Calculator
Screening-level plumbing takeoff: fixture units, water tank count, cold/hot water pipe length, drainage pipe length.
FU = Units × FU/unit · Tank = ceil(Units × FU/unit × 0.8 / 1000) · Pipe = Floors × Run per floor MEP Mechanical (HVAC) Calculator
Screening-level HVAC takeoff: air volume, cooling load, AHU count, duct length, diffuser count.
Air Volume = Area × Height × ACH · Cooling = Area × W/m² · AHUs = Floors · Duct = Area × Ratio · Diffusers = Units × per Unit Fire & Life Safety Calculator
Screening-level fire protection takeoff: sprinkler heads, riser length, hydrant count, extinguisher count, alarm device count.
Heads = Area / Coverage · Riser = Floors × 3.2 · Hydrants = Perimeter / Spacing · Extinguishers = 2 × Floors · Alarms = 2 × Units Finishes & Facades Calculator
Screening-level finishes takeoff: plaster volume, paint area, tile area, glazing area, flooring area.
Plaster = Wall Area × Thickness · Paint = Wall Area · Tiles = Sellable × Ratio · Glazing = Sellable × Ratio · Flooring = Sellable Site Infrastructure & External Works Calculator
Screening-level external works takeoff: paving area, drainage length, landscaping area, fencing length, street light count.
Landscaping = Site × Ratio · Paving = Site − Footprint − Landscaping · Drainage = Site × Ratio · Fencing = 4 × √Site · Lights = Fencing / Spacing Testing & Commissioning Calculator
Screening-level testing & commissioning takeoff: test points, commissioning days, instruments.
Test Points = Systems × Points/System · Commissioning Days = Systems × Days/System · Instruments = Systems × Instruments/System Structural Framing Calculator
Screening-level RC framing takeoff: beams, core/shear walls, stair flights, and wall/soffit formwork derived from level count and floor plate.
Beams = Lines/Floor × Length × Levels × Section; Core = Plan Area × Thickness × Levels; Stairs = Risers × Going × Width × Flights; Formwork = Vertical Faces + Soffit Area Basement Works Calculator
Basement structure takeoff: base slab, retaining walls, basement columns, grade beams, ramp decks, tanking, sumps and reinforcement — from the building footprint and perimeter.
Base Slab = Footprint × Thickness × Levels; Retaining Walls = Perimeter × Depth × Thickness × Levels; Waterproofing = Slab + Wall Faces; Rebar = Concrete × kg/m³ Vertical Transportation Calculator
Screening-level lift group sizing from unit population and levels served, with the derived lift shaft construction area.
Population = Units × Persons/Unit × Factor; Cars = Peak Population ÷ (Car Capacity × Rounds per Interval); Shaft Area = Shaft Perimeter × Height × Lifts Envelope, Facade & Roofing Calculator
Geometric facade takeoff from the building perimeter and storey count: glazed area, opaque panels, parapet and roof membrane — not a share of sellable area.
Facade = Perimeter × Storeys; Glazed = Facade × Glazing %; Opaque = Facade × Panel %; Roof = Footprint × Coverage % Electrical Supply & Lighting Calculator
Sizes the transformer and standby generator from a computed maximum demand, plus main switchboards and general/emergency luminaire counts.
Transformer = Max Demand × (1 + Allowance) rounded up to a standard rating; Generator = Max Demand × Critical Share; Luminaires = Lit Area ÷ Area per Luminaire Plumbing Demand & Stormwater Calculator
Demand-based water sizing: storage volume from per-capita demand, booster pump set, hot water demand, and external stormwater flow and outfall size.
Storage = Population × Demand × Drawdown Hours (floored at a minimum); Stormwater = Contributing Area × Rainfall Intensity; Outfall rounded up to a standard diameter Fire Water & Egress Calculator
Occupant load, fire water storage from flow × duration (floored at a minimum), duty/standby pump sets, escape stair count and rated fire doors.
Occupant Load = Total GFA ÷ Occupant Density; Tank = Flow × Duration (floored at minimum); Pumps = Zones × 2; Doors = Stairs × Levels Served Sodium Metabisulphite Dosing Calculator
Dose sodium metabisulphite from the chlorine residual it must neutralise or the sulphite level it must hold, using the stoichiometric ratio and your product strength. No chlorine residual and no product strength are assumed.
SMBS = Cl₂ demand × 190.12/70.90 (1 mol each), or sulphite target ÷ 2 (1 mol SMBS yields 2 mol SO₃²⁻) · product mass = active ÷ the certificate assay when one is given, else ÷ nominal strength — the assay replaces the strength, never both · no finished pH is predicted Coagulant Dosing Calculator
Turn a jar-test coagulant dose into active metal and product mass per day, from the dose basis you measured and the product active content. The dose is your jar test and the pH outcome is not predicted.
active metal (kg/h) = Q × dose ÷ 1000 · product (kg/day) = active ÷ active content · safety factor applies to both so they cannot disagree · no pH is predicted Clarifier Sizing Calculator
Size a circular or rectangular clarifier from the surface overflow rate, then check it against the solids loading when you state both. Reports which criterion governs and never predicts a solids removal.
area = Q ÷ SOR · load-based area = (Q × 24 × SS × removal%) ÷ (1000 × capacity) · governing criterion is reported · detention time is a consequence, not a criterion Activated Sludge Sizing Calculator
Size an aeration basin from the applied COD load, the F/M loading and the MLVSS, then audit your stated SRT, HRT and volume against each other. Reports oxygen demand as demand only, never as air flow.
load = Q × S₀ ÷ 1000 · V = load ÷ (F/M × X) on the APPLIED load · Px = Yobs × load removed · θc = VX ÷ Px · wasting = inventory ÷ θc · O₂ = 8/7 × COD removed, +4.57 per kg NH₄-N removed · air flow is not calculated GAC Contactor Sizing Calculator
Size a granular activated carbon bed from the empty bed contact time you selected, giving the bed volume, media mass and backwash shell volume. Breakthrough and contaminant removal are not predicted.
bed volume = Q × EBCT ÷ 60 · media mass = bed volume × bulk density · backwash shell = bed volume × (1 + expansion) · breakthrough and removal are NOT predicted UV Disinfection Sizing Calculator
Size a UV reactor bank from the required dose and design flow, then count parallel reactors against the out-of-service allowance. The ideal power is stated separately from the validated reactor power.
required power = Q × dose (1 mJ/cm² over 1 m³/h is 1 W) · reactors = ceil(required ÷ (module power × duty factor)) · annual energy is nameplate × availability CIP Tank Sizing Calculator
Size CIP cleaning and storage tanks from your cleaning protocol volume per element and the heel the tank retains, with separate alkaline, acid and neutral volumes and optional annual chemical consumption.
cleaning volume = elements × protocol volume per element · tank volume = cleaning volume ÷ (1 − heel) because the heel is retained · annual chemical = mass × cleanings per year Brine Volume and Mass Calculator
Annualise the brine volume and salt mass from the concentrate stream, with optional disposal cost and the dilution arithmetic against a stated permit limit. No compliance verdict is issued.
annual volume = brine flow × operating hours · salt mass = TDS × volume ÷ 1e6 to tonnes · dilution = Q × (C − limit) ÷ limit · no compliance verdict is issued Voltage Drop Calculator
Calculate conductor voltage drop and the voltage actually delivered to the load for single-phase, three-phase and DC circuits.
dV = k x I x R x L, with k = 2 for DC/single-phase and 1.732 for three-phase Wire Sizing Calculator
Size an electrical conductor from both its ampacity and its voltage drop over the run, and see which of the two governs.
R_max = (p/100) x V x 1000 / (k x I x L); the smallest standard size with R <= R_max and ampacity >= I is selected Conduit Fill Calculator
Check electrical conduit fill against the permitted percentage and find the smallest standard conduit that accepts the conductors.
fill% = (n x A_conductor) / A_conduit x 100, limited to 53% / 31% / 40% for 1 / 2 / 3 or more conductors Power Factor Correction Calculator
Calculate the reactive power in kVAr that must be removed with capacitors to reach a target power factor.
Qc = P x (tan acos(pf1) - tan acos(pf2)) Transformer Sizing Calculator
Select the next standard transformer rating from connected load, demand factor and a future growth allowance.
S_standard >= S_connected x demand factor x (1 + growth) Sensible & Latent Heat Calculator
Split an airflow and its temperature and humidity differences into sensible and latent cooling loads.
Qs = 1.08 x CFM x dT ; Ql = 0.68 x CFM x dW (grains/lb) Refrigerant Charge Calculator
Refrigerant charge mass against circuit volume, with superheat and subcooling checked against the bands you supply to flag a floodback or flashing condition.
m = V·ρ; SH = T_suction − T_sat(evap); SC = T_sat(cond) − T_liquid Cooling Tonnage & Airflow Calculator
Convert a cooling load in Btu/h to tons of cooling and to the matching airflow in CFM.
tons = Btu/h / 12,000 ; CFM = tons x cfm per ton Duct Sizing Calculator
Size round and rectangular ducts from airflow and a design velocity, returning the next standard size and the actual velocity.
A = Q / v ; D = sqrt(4A/pi) Cooling Load Calculator
First-pass cooling load from envelope U-values, areas and internal gains, converted to tons and airflow.
Q = sum(U_i x A_i x dT) + 3.412 x internal watts Fan Total Static Pressure Calculator
Total fan static pressure from a schedule of duct, fitting and terminal losses, with the margin against the static you have available and the item carrying most of it.
TSP = sum duct friction + sum fitting losses + sum terminal / plant losses Fan System Curve Calculator
Plot the duct system resistance curve from your design point and see what extra airflow costs, plus what data is still needed for a fan operating point.
dP(Q) = dP_d * (Q / Q_d)^2 Duct Friction & Pressure Drop Calculator
Calculate round duct velocity, Reynolds number, friction factor and pressure drop per 100 ft before selecting a fan.
f = 0.25 / [log10(e/3.7D + 5.74/Re^0.9)]^2 ; dP = f (L/D) rho V^2 / 2 Steel Beam Capacity Calculator
Allowable bending and deflection check for a simply supported steel beam, reporting which criterion governs.
M = wL^2/8 or PL/4 ; Mn = 0.66 x Fy x Sx ; governing load = min(bending, L/240 deflection) Beam Deflection Calculator
Elastic beam deflection for six support and loading arrangements, compared with the L/240 serviceability limit.
delta = k x w L^4 / EI or k x P L^3 / EI, with the limit taken as L/240 Falsework Load Calculator
Falsework load path from slab self-weight and imposed construction load down through the bearer, props and sole boards, checking each step against a capacity you supply.
W = A·h·ρ·g; F_prop = (W·factor + W_imposed) / n Column Buckling Calculator
Euler and Johnson critical loads for a slender column, with the slenderness ratio and the governing formula reported.
Pcr = pi^2 E I / (K L)^2 ; Pjohnson = A (Fy - Fy^2 lambda^2 / 4 pi^2 E) Section Properties Calculator
Area, second moments of area, radii of gyration and section moduli for rectangles, boxes, pipes, I-sections and channels.
I = integral y^2 dA ; r = sqrt(I/A) ; S = I / c Retaining Wall Stability Calculator
Check overturning, sliding and bearing of a retaining wall from Rankine active earth pressure.
Ka = (1 - sin phi)/(1 + sin phi) ; FSo = W B/2 / sum(Pa y) ; FSs = (W tan(2phi/3) + cB) / Pa Anchor Pull-out Capacity Calculator
Check a mechanical anchor against both failure modes — concrete cone breakout and steel tension — and see which one actually limits it.
N_concrete = c * pi * d * L * k | N_design = min(N_concrete, N_steel) Roof Snow Load Calculator
Roof snow load from the ground value and the shape, exposure and thermal coefficients, with the extra force from drifting at an upstand.
p_k = mu * C_e * C_t * s_k Wind Load Calculator
Velocity pressure from the site, then the surface pressure and total force for a shape coefficient you supply for the surface in question.
q_p = 0.5*rho*v^2*c_e ; p = q_p*c_pe ; F = p*A*C_f Seismic Base Shear Calculator
Design base shear as the seismic weight times the response coefficient, with the ductility the structure is allowed to absorb shown alongside.
V = C_s * W Slope Stability Calculator
Ordinary (Fellenius) factor of safety over a circular slip surface built from slices you define, with pore pressure applied to each slice.
FoS = sum(c*L + N*tan(phi)) / sum(W*sin(alpha)) Soil Bearing Capacity Calculator
Terzaghi bearing capacity with the standard shape factors, divided by a global safety factor to give an allowable pressure.
qu = c Nc sc + q Nq + 0.5 gamma B Ng sgamma ; q_all = qu / FS Pile Capacity Calculator
Single pile capacity in clay or sand from skin friction and end bearing, split into components and divided by a safety factor.
Qs = alpha c pi D L ; Qp = Nc c pi D^2 / 4 ; Q_all = (Qs + Qp)/FS Foundation Settlement Calculator
Estimate immediate elastic settlement and one-dimensional consolidation settlement beneath a footing.
de = q B (1 - nu^2) If / E ; sc = Cc H /(1+e0) log10((s0 + ds)/s0) Soil Voids Ratio Calculator
Derive void ratio, porosity, degree of saturation and the dry, saturated and submerged unit weights from bulk unit weight and water content.
e = (Gs gamma_w (1+w) / gamma) - 1 ; n = e/(1+e) ; Sr = w Gs / e Differential Settlement Calculator
Angular distortion and differential settlement along a row of footings, from your reference settlement and bearing pressures, finding the worst local pair rather than the end-to-end average.
s = (σ/σ_ref)·s_ref; Δ/L = |s_j − s_i| / L (local pairs) Earth Pressure Calculator
Rankine active and at-rest horizontal earth pressure with surcharge, resultant thrust and the height at which it acts.
Ka = (1-sin phi)/(1+sin phi) ; K0 = 1 - sin phi ; Pa = 0.5 gamma H^2 Ka + q Ka H Culvert Capacity Calculator
Full-flow culvert capacity and velocity from the Manning equation, or the smallest barrel that passes a design flow.
Q = (1/n) A R^(2/3) S^(1/2) with R = D/4 for a full circular barrel Culvert Scour Calculator
Local scour hole depth at a culvert inlet from the HEC-18 inlet shear relation, with the live-bed alternative reported separately rather than added to it.
u* = C_d·v·√g; τ_c = θ_c·ρ_w·(s−1)·g·D50; y_s = 0.325·(y_t·D50/τ_c) Storm Drain Sizing Calculator
Select the smallest standard storm drain pipe that passes the design flow and check the self-cleansing velocity.
Q = (1/n) A R^(2/3) S^(1/2) with a minimum velocity check of about 0.75 m/s Detention Basin Calculator
Detention storage volume and pond footprint from the peak inflow, the permitted discharge and the design storm.
Q = 2.78 C i A ; V = (Qin - Qout) t Asphalt Quantity Calculator
Convert plan area and layer thickness into asphalt volume, tonnage and the number of tipper deliveries needed.
V = A x t ; m = V x density x (1 + waste) Pavement Layer Calculator
Required flexible pavement thickness from wheel load and section modulus, split into wearing course, base and sub-base by the equivalency factors you supply.
ε_z = 1.5·q_v/E_p · 1/√(1+(h/a)²); h = a·√(k²−1) Horizontal Curve Calculator
Circular curve geometry from the deflection angle and radius, with a speed check from superelevation and side friction.
T = R tan(d/2) ; E = R(sec(d/2) - 1) ; M = R(1 - cos(d/2)) ; V = sqrt(gR(e+f)) Drainage Fixture Unit Calculator
Total drainage fixture units and the minimum building drain from fixture counts under the IPC or UPC tables.
Total DFU = sum(n x DFU) ; building drain from the code sizing table Water Supply Fixture Unit Calculator
Total water supply fixture units converted to an estimated peak demand in gallons per minute and a typical service size.
Total WSFU = sum(n x WSFU) ; peak demand interpolated from the Hunter flush-tank curve Septic Tank Sizing Calculator
Septic tank volume and standard size from residents, daily flow, retention time and the sediment storage allowance.
V = n x q x (t/24) x sediment factor Rainwater Harvesting Calculator
Annual and monthly rainwater yield from a roof, with a cistern size derived from a daily demand and autonomy period.
V_year = A x (P/1000) x C x efficiency Sump Pump Sizing Calculator
Inflow to a sump from the drainage area and design rainfall, with the safety-factored pump capacity and hydraulic power.
Q = A x (i/1000) x C / 3600 ; P = rho g Q H / eta Condensate Line Calculator
Condensate drain line sizing including the flash steam released as hot condensate drops to atmospheric, checked against the gravity capacity of the line at the slope you enter.
f_flash = h_fg/(h_fg + c_p·ΔT); load = m·(1−f_flash)·(1+S) Compressed Air Receiver Sizing Calculator
Size an air receiver and find how much free air it releases over the pressure swing, the run time it gives the network, and the volume a required run time needs.
V_free = V x (P1_abs - P2_abs) / P_atm Water Hammer Surge Calculator
Surge pressure from a valve closure or pump trip, with the rapid-closure (Joukowsky) and slow-closure regimes separated by the pressure-wave round trip.
dP = rho*a*dV (t <= 2L/a) | 2*rho*L*dV/t (t > 2L/a) Expansion & Pressurisation Vessel Sizing Calculator
Size the vessel that absorbs a closed water loop’s thermal expansion, with the usable pressure fraction and the pre-charge the sizing depends on.
V_t = (beta * dT * V_s) / (1 - P1/P2) Sprinkler Branch Hydraulic Calculator
Pressure balance along a sprinkler branch from Hazen-Williams friction loss, with the residual at the riser end and at the most remote head checked against the band you enter.
h_f = 10.67·L·Q^1.852/(C^1.852·d^4.87); Q = K·√P NPSH Calculator
Net positive suction head available at the pump from pressure, vapour pressure, static head and suction friction.
NPSH(A) = (Pa - Pv)/(rho g) + Hs - Hf Pipe Fitting Loss Calculator
Head loss, pressure drop and equivalent length for a pipe fitting from its K-value and flow velocity.
hL = K V^2/(2g) ; Le = K D / f LMTD Calculator
Log mean temperature difference for a counter-flow heat exchanger and the heat transfer area it implies.
dTlm = (dT1 - dT2)/ln(dT1/dT2) ; A = Q/(U F dTlm) Pipe Thermal Expansion Calculator
Free linear expansion of a pipe run for a given material, length and temperature rise, in millimetres and per 100 m.
dL = alpha x L x dT Weir Flow Calculator
Discharge over rectangular, contracted, V-notch and Cipolletti weirs from the head above the crest.
Q = 1.84 L H^1.5 (rectangular) ; Q = 1.38 H^2.5 (90 degree V-notch) Energy Load Audit Calculator
Convert appliance watts and daily running hours into a daily energy demand in watt-hours and kilowatt-hours.
E_day = sum(W_i x h_i) Solar Array Sizing Calculator
Number of photovoltaic modules needed for a daily energy demand from peak sun hours and a system derating factor.
P_array = E_day / (PSH x (1 - derate)) ; n = ceil(P_array / P_module) Battery Bank Sizing Calculator
Storage energy and ampere-hours for a daily demand, autonomy period and depth of discharge, with the series and parallel layout.
E_bank = E_day x days / DoD ; Ah = E_bank / V Inverter Sizing Calculator
Continuous and surge inverter rating from the largest load, a load-type surge factor and a design margin.
P_cont = P_load x (1 + margin) ; P_surge = P_load x surge factor Solar Thermal Collector Area Calculator
Size a flat-plate solar thermal collector from a heat balance — once for the daily hot water demand and once for the peak hour — and see which one actually governs.
q_u = eta0*G - U_L*(Tabs - Tf) | A = max(daily energy sizing, peak hour sizing) Crane Lift Calculator
Static sling leg tension for a bridle lift, with the 1/cos(b) angle rise kept separate from the per-leg share and the rigging efficiency applied for 3 legs or more only.
T_leg = W / (n · cos β); efficiency divided in for n ≥ 3 Charge Controller Sizing Calculator
Charge controller current rating from array watts and battery voltage, with MPPT or PWM correction and 25 % headroom.
I = P_array / V_battery ; I_controller = I x 1.25 Greywater Reuse Calculator
Reusable greywater available per day and the storage volume needed, from residents, laundry flow and the captured fraction.
Q_reuse = (n x q_person + q_laundry) x capture fraction Irrigation Demand Calculator
Daily and weekly irrigation water requirement from reference evapotranspiration, crop factor and system efficiency.
V = A x (ET0 x Kc) / (1000 x efficiency) Infiltration Trench Calculator
Length and drain time of an infiltration trench from the stored runoff volume, void ratio and soil infiltration rate.
V = A x P x C ; V_trench = V / void ratio ; t = V / (k x base area) Soakaway Calculator
Soakaway storage and base area from a percolation test result, the drainage area and the design storm.
k = 1000 / percolation time ; V = A x P x C ; A_base = V / depth Bioswale Calculator
Trapezoidal bioswale geometry, storage volume, media void storage and drawdown time for a given infiltration rate.
A = (b + z d) d ; V = A L ; t = V / (k P L) Concrete Formwork Pressure Calculator
Lateral formwork pressure for a concrete pour from placement rate, temperature and unit weight, capped at the hydrostatic head.
p = Cw Cc (7.2 + 785 R/(T + 17.8)), capped at the fresh lift hydrostatic head Concrete Block Wall Calculator
Block count and bedding mortar quantity for a block wall, with an opening deduction and a waste allowance.
N = A_net x 12.5 blocks/m2 ; mortar = A_net x 0.028 m3/m2 Rebar Development & Splice Calculator
Tension development length and Class A and B lap splices for a bar diameter, steel grade and concrete strength.
ld = (fy x psi_t x psi_e x psi_s) / (2.1 x lambda x sqrt(fc)) x db Staircase Concrete Volume Calculator
Concrete volume of a reinforced concrete staircase, split into waist slab, steps and landing.
L = sqrt((n g)^2 + (n r)^2) ; V = L t w + n (0.5 r g w) Chloride Ingress & Cover Durability Calculator
Fickian chloride diffusion to the reinforcement, reporting the time to corrosion at your cover and the cover needed for the design life.
C(x,t) = Cs * erfc(x / (2*sqrt(D*t))) Plaster & Screed Volume Calculator
Plaster volume, dry mix volume, cement bags and sand quantity for a given area, thickness and mix ratio.
V_wet = A t ; V_dry = 1.33 V_wet ; cement = V_dry x kg per m3 of the chosen mix Waterproofing Takeoff Calculator
Measured-area takeoff for waterproofable surfaces, with declared layer counts. Material quantity stays unresolved until a product coverage rate is supplied.
A = L x W per surface ; area to treat = total measured area x declared layers ; units = area / user-entered coverage Joinery & Metalwork Schedule Calculator
Count and dimension schedule for doors, windows, handrails, balustrades and metal frames. Quantity takeoff only, not a manufacturing specification.
Count ; area = count x width x height ; balustrade area = run length x height ; frame length = count x frame length No matching calculators found
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