Heating, Ventilation & Air Conditioning Calculators
Cooling loads split into sensible and latent parts, tonnage and airflow conversion, duct sizing and duct friction — the first-pass checks for air distribution design.
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