Quantity take-off
Quantity take-off from drawings: manual, software and AI
Published:
Compare manual, on-screen and AI-assisted quantity take-off, what each needs from the drawings, and how to check quantities before pricing.
Original guide. CAIS QTO is experimental and needs independent validation. Nothing here states an accuracy figure for any method.
Three ways to take off quantities
Each method can produce a good BOQ; each fails in its own way.
| Method | How it works | Watch for |
|---|---|---|
| Manual | Scaling and counting from prints or PDFs, with dimension sheets. | Slow work; arithmetic and transcription errors. |
| On-screen software | Tracing areas, lengths and counts over the drawing on screen. | A wrong scale calibration; items traced twice. |
| AI-assisted | Software proposes counts and measurements from the drawing or model. | Missed or invented items; every result checked against the drawings. |
What every method needs from the drawings
No method recovers information the drawings do not contain.
- A stated scale and the current revision.
- Legends and schedules that define symbols, finishes and fittings.
- Sections and details for depths, thicknesses and heights.
- A named measurement standard for the BOQ.
The measurement rules decide the quantity
The same drawing gives different quantities under different rules: whether openings are deducted, how laps are treated, where one item ends and the next begins. State the standard the BOQ follows, for example POMI, NRM2 or CESMM, and apply it the same way throughout.
Check the quantities before pricing
A quantity error carries straight into the price.
- Compare totals with a quick independent estimate: floor areas, wall lengths, typical ratios.
- Re-measure a sample of items by hand on the drawings.
- Look for items with zero or implausible quantities.
- Record every change with its drawing reference.
Where CAIS fits
CAIS offers experimental QTO from PDF, IFC and DXF drawings, with separate pages for MEP and infrastructure. Treat its quantities as a draft for a quantity surveyor to check before they are priced.