Check a Sewing Pattern PDF Scale Before You Cut Fabric (Test Square)

A print-at-home sewing or craft pattern is only as good as its scale. If it prints 3% small, every piece is 3% small and the garment will not fit. Most patterns include a test square for exactly this reason. Here is how to check it, and how to confirm the PDF itself is true.

Step 1: print at 100% and measure the test square

Print the first page only, with the scale on Actual size or 100% and any Fit to page or Shrink to fit option off. Measure the test square on the page with a physical ruler. It is usually 10 cm or 4 inches (about 101.6 mm) on a side. If yours is off, the printer scaled the page. No test square? Print the print at actual size test sheet instead; it has 100 mm and 4 inch marks.

Step 2: confirm the PDF is not the problem

Open the pattern in PdfRuler, set the unit to mm or inches, and measure the test square with two clicks, or turn on Pick and click it. If it reads 100 mm in the PDF but 96 mm on paper, fix the print settings. If it reads 96 mm in the PDF, the file was exported at the wrong size, so contact the designer.

Letter or A4?

Many patterns ship with both an A4 and a US Letter file. Use the one that matches your paper. A Letter file on A4 paper may be shrunk or have its edges cut off. Compare the page size with the A4 and US Letter references, and read how the two differ.

Assembling tiled pages

Large pieces are tiled over several pages. The tiles line up only if every page printed at the same true scale, so measure one square on every sheet before you start taping. The point tool and guides help you check seam allowances and alignment marks in the PDF.

Fix a wrong scale

Divide the correct length by the measured length and multiply by 100. A 4 inch square that measures 3.9 inches needs 102.6%. Reprint one page at that custom scale and re-measure. More on rescaling: why PDFs print smaller than 100%.

Frequently asked questions