TRIMCRAFT

Pattern Scaling Calculator

Compare your measurement to a pattern's stated size to get the exact scale factor and printer percentage — and see what should stay fixed while everything else scales.

E.g. your actual bust/waist/hip measurement at the spot the pattern measures.
The finished or body measurement the pattern lists for that same spot, from its size chart.
Any traced length on the pattern piece — this shows what it becomes at the new scale.
Shown for reference — seam allowance does NOT scale with the pattern.

Scale this pattern

Scale factor
1.1111×
Copier / PDF scale-to-fit setting
111.1%
Scaled pattern-piece dimension
11.111 in
Seam allowance (unchanged)
0.625 in

One ratio, applied consistently

Scaling a paper pattern comes down to a single ratio: your measurement divided by the pattern’s own stated measurement at that same spot. Multiply every traced dimension on the pattern piece by that ratio and the whole shape grows or shrinks together, keeping its proportions intact. The same ratio, expressed as a percentage, is exactly what a photocopier zoom or a PDF reader’s custom print-scale field expects — punch in the percentage instead of leaving it on a default 100% or “fit to page.”

The one deliberate exception is seam allowance. It is added at a fixed width during cutting, not as a proportion of the garment, so it should stay exactly as printed regardless of how much the rest of the pattern scales — scale the stitching line and the outline, then re-add the same constant seam allowance around the newly scaled shape.

Frequently Asked Questions

How do I turn a scale factor into a photocopier or printer setting?

Multiply the scale factor by 100. A factor of 1.111 becomes 111.1% — that's the number you type into a photocopier's zoom setting or a PDF reader's custom "scale" or "print at" field instead of the default "fit to page" or "100%" option.

Why shouldn't seam allowance scale with the pattern?

Seam allowance is a fixed width added during cutting so a seam can be sewn and pressed — it isn't a proportion of your body or the garment. If you scale the whole pattern piece including its printed seam line by, say, 111%, the seam allowance itself grows too, which throws off exactly how much fabric turns under at the seam. Scale only the pattern's shape (the stitching lines and the overall silhouette) and keep the seam allowance at its original constant width.

What's the difference between scaling and grading?

Scaling multiplies every dimension by the same ratio — it works best over a small range, close to the pattern's original size, because a body doesn't grow perfectly proportionally in every direction. Grading (moving between standard pattern sizes) instead adds a fixed increment at each size step to specific reference points, which is why multi-size patterns include a separate line for every size rather than one shape stretched by a ratio.

Is scaling a safe way to resize a pattern several sizes at once?

It works reasonably well for a size or two, but a straight scale-factor multiplication starts to distort fit noticeably over a larger range, because armholes, necklines, and other curved details don't grow at the same rate as a straight bust or waist measurement. For a bigger jump, a properly graded multi-size pattern or a pattern specifically drafted to your measurements will fit better than pure scaling.

Educational tool only. Scaling works best over a size or two; for a larger resize, a properly graded multi-size pattern will usually fit better.