Manual Tools

Scale Calibration

Calibrate the drawing scale so that all measurements (linear and area) reflect real-world dimensions. You can select a common architectural scale preset or calibrate manually by measuring a known distance on the drawing.

Steps

1. The scale selector is the leftmost control in the viewer toolbar. It reads "Set Scale" until a scale is chosen.
2. Select a preset scale if you know the drawing scale. The architectural presets run from 1/16" = 1'-0" up to 3" = 1'-0", and the engineering presets for civil and site plans from 1" = 10' to 1" = 100'. A preset assumes the PDF page is the printed sheet size, which shows next to the scale; for a scan or a half-size set, calibrate from a known dimension instead.
3. Or choose "Custom..." to type the scale directly (inches and feet fields appear next to the dropdown).
4. To calibrate manually, choose "Calibrate..." from the dropdown.
5. A PNG or JPG that carries no resolution information has no paper size, so picking a paper scale on it asks for the sheet's printed width first (or Calibrate instead). The width is kept with that sheet. Measuring stays locked until the chosen scale resolves to a real value: a custom scale that cannot be read shows why under the inputs.
6. In the "Calibrate Scale" dialog, enter the known measurement in the ft. and in. fields, then press Enter or click Apply.
7. The dialog closes and prompts you to click the two points of the known distance on the drawing (e.g., endpoints of a dimension line).
8. The scale is calculated automatically and displayed in the selector (e.g. 0.125" = 1').

Notes

• •Measurement tools and Auto Takeoff are blocked until this sheet's scale is confirmed. The toolbar buttons open a pop-out on the Scale selector that says "Set the scale before starting any takeoff", and the keyboard shortcuts show "Confirm the drawing scale first". On a sheet without a scale, the Auto Takeoff menu still opens when another sheet that is not hidden or rotated has its own scale, so "Multiple sheets…" can run the sheets that do; its choices for this sheet show the same pop-out.
• •The scale applies to the entire sheet, and different sheets can have different scales. Every quantity uses the scale of the sheet it is on. Set the scale on each sheet: a sheet you have not set one on shows Set Scale, and measuring and Auto Takeoff wait until you pick its scale.
• •Recalibrating recomputes existing lengths and areas on the sheet from their geometry. Counts are unaffected.
• •If the drawing includes a graphic scale bar, you can use it for calibration.