Setting the scale

Scale is the one setting that can make every number in a take-off wrong at once, and the one nothing on screen will warn you about. It is worth ten seconds of care.

Scale is set per page, not per drawing. A 1:20 detail and a 1:200 site plan routinely live in the same PDF, and Take-Off handles that properly.

Standard ratios

If the drawing states its scale and you trust it, pick the matching ratio from the Scale dropdown. This is right the overwhelming majority of the time for native PDFs issued straight from CAD.

Then check it anyway. Find a figured dimension on the sheet, drag the Line tool along it, and confirm you get the number that is printed. If you do, the page is scaled correctly and you can measure with confidence.

Custom scale (calibration)

Choose Custom… from the dropdown, then drag along something on the drawing whose real length you know — a gridline spacing, a figured dimension, a door opening. Type in what that distance actually is, and Take-Off works out the scale from it.

Calibrate rather than trusting the printed ratio when:

• the drawing has been scanned or photocopied;
• it has been printed to a different sheet size — an A1 drawing issued as A3 is no longer at its stated scale;
• the stated scale simply looks wrong when you check a known dimension.

Calibrate along the longest dimension you can find

Any error in where you click is divided by the length you drag, so a 10 m gridline gives a far better result than a 900 mm door. If the only figured dimension is short, calibrate across several grid bays at once and enter the total.

Horizontal and vertical are calibrated separately

Take-Off calibrates the horizontal and vertical directions independently. That matters for scans, which are often very slightly stretched in one direction — a drawing that measures correctly across but 1% out vertically will still give you correct areas.

It is also the fix for the classic scan symptom: areas that look right while lengths do not, or the reverse.

Worked example: calibrating a scanned drawing

A client sends a PDF that is clearly a scan of a printed A3 sheet. The title block says 1:100, but you have no idea what size it was printed at.

1. Choose Custom… from the Scale dropdown.
2. Find the longest figured dimension on the sheet. Here it is the overall building width, marked 14 600.
3. Drag from the outside face of one external wall to the outside face of the other, following the dimension line.
4. Take-Off asks what that distance really is. Type 14.6 and choose metres.
5. Repeat vertically when prompted, using the overall depth dimension — say 9 200, entered as 9.2.

Take-Off now reports the derived scale, which might come out at something like 1:141 horizontally and 1:139 vertically. Those are not tidy numbers, and that is exactly the point: the sheet was never at a tidy scale, and guessing 1:100 would have made every quantity roughly 40% light.

Re-scaling a page you have already measured

Changing the scale of a page recalculates every measurement on it. That is almost always what you want — if the scale was wrong, every number taken off that page was wrong too.

But it also means quantities already in your BOQ will move. Take-Off asks you to confirm first, and tells you how many measurements will be affected.

Caution

Read that confirmation. “Re-scaling will update 62 measurements across 4 fields” is telling you that four BOQ quantities are about to change. If that is a surprise, stop and work out why before you continue.

Pages without a scale

Counting works on an unscaled page. Counting doors does not need a scale, so the Count tool is available immediately.

Lengths and areas do need one, so those tools stay disabled until the page is scaled. Hover over a disabled tool and it will tell you why.

Common problems

Every quantity on a page is wrong by the same factor. The page scale is wrong. Check it against a figured dimension; if the drawing has been re-sized or scanned, calibrate rather than using the printed ratio. Re-scaling the page fixes every measurement on it at once.

Areas are right but lengths are wrong, or the reverse. Almost always a stretched scan. Re-calibrate with Custom… — Take-Off measures the horizontal and vertical independently and will correct it.

The Line, Polyline or Area tool is greyed out. Usually the page has no scale yet. Hover the tool and the tooltip will say so.