🖨️ Pattern Scale Percentage Calculator

Enter a known dimension on your pattern (like a printed test square) and the dimension you want it to be, to find the percentage to set on your printer or copier.

Original pattern dimension (in)

Desired final dimension (in)

The percentage is one ratio

scale % = desired dimension / original dimension x 100

The defaults, 1 in to 1.5 in, give 150.0%. The usual real job is smaller: a test square that should be 4 in prints at 3.85 in, so 4 / 3.85 = 103.9% and you reprint at that setting. Measure the square, not the page.

What scaling does to the rest of the sheet

Seam allowances scale too. A 5/8 in allowance printed at 150% arrives at 0.94 in, and at 103.9% it becomes 0.65 in. If you sew to a fixed guide on the machine bed, note the new width or trim the allowance back to 5/8 in before cutting.
Area grows by the square. 150% makes each piece 2.25 times the area, so a 2 yd layout needs about 4.5 yd. Check the fabric before committing to a large enlargement.
Mind the paper. An A4 tiled pattern printed on Letter with fit-to-page lands near 94% - small enough to look right and wrong enough to ruin the fit. Set actual size, then measure.

Scaling is not grading. A percentage multiplies every dimension at once - armhole depth, neckline, dart legs and shoulder width along with the bust - while a size grade adds width where the body changes and leaves the rest close to the original. Use this tool to correct a print, not to move between sizes.

Frequently asked questions

How do I fix a pattern that printed the wrong size?

Measure the printed test square, divide the size it should be by the size it came out, and multiply by 100. A 4 in square that printed 3.85 in needs 103.9% on the reprint, entered as a custom scale rather than fit-to-page.

Can I print a pattern larger to get a bigger size?

Not sensibly. Enlarging to 110% adds 10% to the armhole, the neck and the sleeve length as well as the bust, so the garment comes out of proportion. Add width at the grade lines instead.

What percentage converts A4 pattern pages to US Letter?

Around 94% if you let the printer fit the page, because Letter is shorter than A4 - and that shrinks the pattern. Print at 100% and let the artwork tile across the extra sheets instead.