Pattern Scale Checker
Print the first page, measure the test square, and find out if you need to reprint — and at what percentage.
Most patterns include a 1" or 2" (2.5 or 5 cm) test square on the first page. Print that page and measure the square before printing the rest.
Why scale errors happen
The most common cause is the PDF viewer's default print setting — "Fit to page," "Shrink to printable area," or similar. These silently scale the PDF down so it fits within the printer's non-printable margin zone. On US Letter paper, this typically results in printing at around 96–97% instead of 100%.
A 3% error sounds small, but on a pattern piece that's 20" across, it means the cut piece comes out at 19.4" — a ⅝" loss. On a 40" circumference (waist or hip), it's 1.2" smaller than expected.
Always use Actual Size or 100%in your PDF viewer. In Adobe Reader, it's under Page Sizing & Handling → Size → Actual Size. In macOS Preview, uncheck "Scale to fit."
No test square on the pattern?
Some older or scanned patterns don't include a calibration square. In that case, measure a straight seam allowance line (if the SA is noted, e.g. ⅝") or a clearly stated measurement on the pattern piece (e.g. a grainline marked as 8"). Use that as your reference.