Getting from a calculator result to a bill of quantities
The path from an engineered quantity to a priced line item, and where quantities get lost between disciplines.
The engineering question
The calculation is right but the bill is wrong. Which quantities are being lost between design and take-off?
Worked example
The figures below were produced by running the Asphalt Quantity Calculator with the same inputs — during the build, from its authoritative engine.
| Tonnage to order | 484.1 t |
|---|---|
| Compacted volume | 200 m³ |
| Tonnage before waste | 470 t |
| Deliveries (20 t) | 25 no |
| Assessment | 200.0 m³ compacted layer weighs ≈ 470.0 t (484.1 t with 3% waste) — plan ≈ 25 20-t deliveries. |
- The calculator produces a net engineered quantity with a stated waste allowance.
- That quantity has to reach the take-off without being re-measured from the drawing.
- The workflow tool carries the same quantity into the bill so it is priced once.
Sanity check
If the bill quantity differs from the calculator output, one of them has been re-measured. They must be traceable to the same source.
Tools for this problem
These are the EngiMetric calculators that compute the numbers in this topic. Each one shows its formula, its units and its limits rather than returning a bare result.
- 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.
- Asphalt Quantity Calculator Convert plan area and layer thickness into asphalt volume, tonnage and the number of tipper deliveries needed.
- Asphalt Quantity Calculator Convert plan area and layer thickness into asphalt volume, tonnage and the number of tipper deliveries needed.
References & standards
- RICS — Standard Method of Measurement
- BCIS — dimensions and setting out
Related problems
Taking off concrete volumes without mis-ordering the pour
Where concrete volume actually goes — including the parts that are habitually forgotten — and how wastage and batching affect the order.
Also: Civil & Structural
Asphalt quantities: from plan area to tipper loads
Converting area and layer thickness into compacted volume, tonnage and the delivery schedule behind it.
Also: Civil & Structural
Blockwork quantities: blocks, mortar and the waste you actually incur
Block counts per square metre, opening deductions, mortar volume and a realistic waste allowance.