How do I do an on-screen take-off from a PDF drawing?
On-screen take-off means measuring quantities straight off a drawing on your computer or tablet instead of with a scale rule on paper. You set the scale, check it against a dimension you know, then click out lengths, areas and counts.
On screen or on paper
With a paper drawing you lay a scale rule along a wall, read the distance, work it up by hand and add the totals yourself. On screen you tell the software the scale, then click along a wall for a length, round a room for an area, and on each door for a count. The totals add up as you go and a wrong click is simply undone.
The figures are still only as good as the drawing and the scale. Our guide on how to do a take-off covers the order of work, deductions and waste; this one is about doing it on screen. It is spelt take-off, takeoff and take off, and digital take-off means the same thing.
What you need
A PDF of the drawing, ideally the one the designer sent rather than a scan or a photo of a printout, with its revision letter. You also need a way to know the scale: a scale bar on the sheet, or a stated scale and the paper size it was drawn for, such as 1:50 at A1. For planning applications in England, GOV.UK says drawings must have an identified scale and that a linear scale bar is useful, particularly for electronic submissions.
A scale bar is the better guide on screen, because it changes size along with the drawing. The words "1:50" are only true at the paper size the drawing was made for.
Set the scale, then check it
Calibrate on the longest clear dimension you can find: a scale bar, or a written dimension on a straight line. Then check against a second written dimension elsewhere on the sheet, ideally at right angles to the first. If they agree, the scale is right across the sheet. If they do not, find out why before you measure anything. If a sheet carries several views, such as a plan at 1:50 and a detail at 1:10, set the scale for each view.
The common mistake is a drawing made at A1 that has been printed or saved to A3. A1 is twice as long and twice as wide as A3, so a drawing marked 1:50 now reads at 1:100. A wall written as 6,000 mm is 120 mm long on the A1 sheet at 1:50, but 60 mm at A3, and software still set to 1:50 reads that as 3,000 mm. Checking against a written dimension catches this in seconds. Our guide on measuring a PDF drawing to scale goes through the steps.
Lengths, areas and counts
- Lengths: click along walls, skirting, pipe runs or fascias. A plan shows flat lengths, so allow for rises, drops and bends separately.
- Areas: click round the corners of a floor, wall or roof. Measure an opening as its own shape and deduct it. A pitched roof or a stair is bigger than it looks on plan, so use the section or the pitch.
- Counts: click each door, window or socket, with a different marker for each type, then check the total against the schedule.
Measure net quantities. Wastage allowances are the estimator's call, because they depend on the material, the cuts and how it is sold, so keep them in a separate column. Our guide on bricks per square metre turns a wall area into bricks and blocks, and the one on what to put in a building quote covers where the figures end up.
Keep the marked-up drawing
Save the marked-up PDF with the job, with the drawing number, revision and date in the file name, and the list of quantities beside it. If a client queries a figure, or a new revision arrives, you can see what you measured and which lines to recheck.
Where it stops being reliable
- Drawings marked "not to scale" or "do not scale": use the written dimensions. Scaled figures are fine for estimating, but check anything critical with the designer.
- Out-of-date revisions: confirm the current revision in writing before you price, and note which one you used.
- Photos: a photo of a drawing or a building is not taken square on, so the scale changes across the image. Treat it as a rough guide, not a measurement.
- Scans and copies: these can shrink or stretch the sheet, so check against a written dimension in both directions.