Free tool · runs in your browser
PDF Scale Calculator — Find the Scale of Any Drawing
Find the scale of a PDF drawing from a single known dimension — measure the printed length, enter the real size, and get the scale ratio and calibration factor. Free.
No signup · nothing uploaded · Free — unlimited use, runs entirely in your browser
How it works
Measure a known dimension
On the printout, or on screen at 100% zoom — door, grid bay, dimension string.
Enter the real size
What that length represents in the world, in feet and inches.
Get the scale
The ratio, the closest standard scale, and the calibration factor.
Every unlabeled or rescaled drawing has a recoverable scale. Measure a known dimension on the printed sheet or on screen at 100% zoom — a door, a grid bay, a dimension string — enter the real-world length it represents, and the calculator returns the drawing scale (1:48, 1/4"=1'-0", etc.), the closest standard scale, and the calibration factor to feed your measurement tool.
This is exactly the calibration step PDFDepth performs on the drawing itself — there you click the two endpoints of a known dimension and the scale applies to every measurement on the page.
Questions, answered
Measure any element with a known real size — a 3'-0" door, a 25' grid bay, a stated dimension — and divide the real length by the measured paper length. A door measuring 0.75" on paper at 3 feet real is 1:48, i.e. 1/4" = 1'-0".
More free tools
Need more than the free limit?
In PDFDepth you click two points on the known dimension and the calibration applies to every measurement on the sheet — verified scale, no math.
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