Free tool · runs in your browser
PDF Scale Detector
Detect architectural and engineering scales like 1/4"=1'-0", 1:100, NTS, and AS NOTED on each sheet of a PDF. Free and private.
No signup · nothing uploaded · No page limit — analysis tools are free for any file size
How it works
Drop in your plan set
Any PDF with a text layer — plan sets, details, schematics.
Scan every sheet
Each page is searched for scale callouts in common formats.
Review the table
Page number, detected scale, and the source snippet for each match.
Drawing sets mix scales — a plan at 1/4"=1'-0", a detail at 3"=1'-0", a schematic marked NTS. This tool reads the text on every sheet and reports which scale callouts it finds, with the surrounding snippet so you can verify each hit.
It reads the title block text, so it only works on PDFs with a real text layer; scans need OCR first. It reports what is written — it cannot verify the drawing is actually printed to that scale. For calibrated measurement and verified scale detection, the PDFDepth app’s Auto-Detect Scale does the full job.
Questions, answered
Imperial scales like 1/4"=1'-0" or 3"=1'-0", metric ratios like 1:100, SCALE: notes, NTS / N.T.S. (not to scale), and AS NOTED.
More free tools
Need more than the free limit?
PDFDepth Auto-Detect Scale calibrates each sheet so you can measure real distances, areas, and angles.
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