How to measure a PDF drawing to scale
Measuring off a PDF is quick for estimating and ordering, as long as the scale is right. Here is how to get reliable figures, and when not to scale at all.
1. Check the scale and the paper size
The title block gives the scale and the sheet size, for example 1:50 at A3. A PDF printed or saved at a different size no longer matches, so 1:50 at A3 printed on A4 is roughly 1:71.
2. Calibrate from a dimension you know
The safest way to set the scale is from a dimension written on the drawing: a room width, a grid line spacing or a scale bar. Measure that line on screen and tell the software how long it really is.
3. Check it against a second dimension
Measure another written dimension a long way from the first. If it agrees, the scale is right across the sheet. If it doesn’t, the drawing may have been stretched, or the dimension may be wrong.
4. Measure what you need
- lengths for walls, kerbs, pipes and skirting
- areas for floors, roofs and plastering, by clicking round the corners
- volumes for concrete and screed: an area times a depth
- counts for doors, windows and fittings
Do not set out from a scaled figure
Most drawings say “do not scale”. Scaled measurements are fine for estimating, take-offs and orders, but set out from written dimensions and check anything critical with the designer.