📏 Pattern Grading Size Increment Calculator

Enter your pattern's base measurement, your target measurement, and how many grade points (cut lines) you're distributing the difference across, to see the adjustment at each point.

Base pattern measurement (in)

Target measurement (in)

Number of grade points

How the per-point adjustment is worked out

total difference = target - base
per grade point  = total difference / number of grade points

With the defaults - 36 in to 40 in over 4 points - the total is 4.000 in and each point takes 1.000 in. The sign is kept: grading down to 34 in returns -0.500 in, so you slash and overlap rather than spread.

Deciding what to type in

Published grade rules give a full circumference change per size - 1 in at bust, waist and hip through the smaller half of a misses range, 1.5 to 2 in through the larger sizes, against vertical rules nearer 1/4 in of back waist length. A piece cut on the fold carries a quarter of a circumference grade: a 2 in bust step is 0.5 in there.

State your seam allowance. Measure base and target the same way. A measured pattern edge includes its allowance - 5/8 in on most pattern company sheets, 1/4 in or 1 cm on indie ones - and a finished measurement does not. Spreading a cut line carries the allowance along unchanged.
Ease is not body. A 40 in target on a jacket is a body measurement plus wearing and design ease. Grade the pattern figure or you lose the ease at every size but the base.

An even split is a budget, not a grade rule. Real rules move each point by its own amount - the side seam takes more than the centre front - so distribute the total, do not assume it lands equally.

Frequently asked questions

How much does a sewing pattern grow between sizes?

About 1 in of bust, waist and hip in the smaller half of a misses range, 1.5 to 2 in in the larger sizes, with lengths changing far less. Grading is not uniform scaling.

Can I print the pattern at a larger percentage instead?

No. Printing at 110% multiplies every dimension, so a bust gain drags the armhole, neckline and seam allowances up with it. Grading adds width only where the body changes.

Why is my pattern size larger than the size I buy in shops?

Commercial pattern sizing is a separate system from ready-to-wear, so two or three sizes of difference is normal. Measure yourself and pick from the chart on the envelope.