Sewing Pattern Grading Calculator
Enter the original pattern size measurements and your target measurements to get the total grade and the amount to add or remove at each seam on each pattern piece. Nothing uploaded.
Grade amounts
| Point | Total grade | Per seam | What to do |
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Learn more: sewing pattern grading and seam adjustments
Why grading is more than just scaling uniformly
Scaling a pattern up 10% across the board makes the armhole bigger, the neckline bigger, and changes the shoulder width in ways that don't match how human bodies actually vary between sizes. Real pattern grading adds specific amounts at specific points - more at the bust, less at the shoulder, different amounts at the hip versus the waist - following the proportional differences between size categories. A size 8 to size 12 difference is not the same as a size 14 to size 18 difference.
How per-seam adjustment works
For circumference measurements (bust, waist, hip), the total grade is divided across 4 seam lines (the two side seams, with both a front and back). Each seam line gets 1/4 of the total grade. For a 4cm total bust grade, each of the 4 seam lines gets 1cm added to both sides. For length adjustments (sleeve, back length), the grade is divided across 2 seam lines (or adjusted as a single line if only center front/back changes).
When to make a fitting muslin before cutting fashion fabric
For small grades (one size up or down), grading confidence is high and you can cut directly into fashion fabric. For grades larger than 2 sizes (approximately 8cm+ at the bust), fit testing is recommended. Make a test garment (muslin or scrap fabric) first, fit it, and check the grade before investing in expensive fabric. The calculator warns for grades over 2 sizes, but it still provides the numbers you need.
FAQ
What is pattern grading in sewing?
Pattern grading is scaling a garment pattern up or down between sizes. Rather than scaling uniformly, grading adds or subtracts specific amounts at specific points - seam lines, dart points, and shaping lines - while maintaining the garment's design proportions.
How much do I add at each seam when grading?
For circumference measurements (bust, waist, hip), divide the total grade by 4 seam lines. For a 4cm bust grade, each seam line gets 1cm. The calculator computes this automatically.
Should I use pattern size or my actual measurements?
Use pattern size measurements (the original garment's stated size) and your target measurements (either your body or the target size's spec sheet). Don't include ease - the calculator doesn't account for design ease.