Sewing Pattern Scale Calculator
Scale percentage
116.7%
How it works
Sewing patterns must often be resized to fit specific measurements or to scale up or down from printed sizes. The Sewing Pattern Scale Calculator computes scaling factors for each body measurement dimension and advises on seam allowance adjustments.
**Why patterns rarely fit perfectly** Commercial patterns are drafted for specific size charts that may not match your body proportions. You may be a size 12 in bust but a size 16 in hips. Pattern grading between sizes addresses this — blending sizes at different measurement points.
**Scale vs. grade** Scaling uniformly (for example, 110% of all measurements) is appropriate for children's patterns or objects like bags and cushions. For garments, grading at specific locations (bust, waist, hips) is more accurate because body proportions do not scale uniformly.
**Enlarging printed patterns** Patterns printed "not to scale" need a reference square to calibrate the photocopy enlargement percentage. If the reference square prints as 3.8 cm instead of 4 cm, you need to scale by 4/3.8 = 105.3% when photocopying.
**Digital patterns** PDF patterns printed at home require testing the calibration square before printing all sheets. Print one page, measure the test square, adjust printer scale, reprint. Tape-together PDF patterns have alignment marks on sheet edges for joining.
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Frequently Asked Questions
- Grading blends between two sizes at specific body measurement points — for example, cutting at size 12 through the bodice but blending to size 14 at the hips. It maintains the design's proportions within the manufacturer's size system. Scaling uniformly enlarges or shrinks all dimensions by the same percentage — appropriate for flat objects (bags, cushions, children's patterns) but problematic for garments because body proportions don't scale uniformly. A person who is 10% taller isn't 10% wider at every point. For garments, grading is almost always preferable to uniform scaling.
- Seam allowances should NOT be scaled — they stay constant regardless of garment size (typically 5/8 inch or 1.5 cm). When scaling a pattern piece that includes seam allowances, you need to: (1) identify the seamline (inside the cut line), (2) scale only the area between seamlines, then (3) re-add the original seam allowance at the new scale. If you scale the entire piece including seam allowances, the seam allowances become either too narrow (risk of fraying) or excessively wide (wasteful). Many sewists prefer to work from seamlines rather than cut lines for this reason.
- Most PDF sewing patterns include a test square (usually 1 inch × 1 inch or 10 cm × 10 cm) on the first printed page. After printing the first page, measure this test square with a ruler. If it measures correctly, your printer is printing at 100% scale. If it measures smaller, your printer scaled down — go to printer settings and ensure 'Fit to page,' 'Scale to fit,' or 'Shrink to fit' is turned OFF. Set scale to 100% or 'Actual size.' Re-print the test page and measure again before printing all pages. Never print without checking the test square — a 5% scaling error across a full garment pattern creates significant fit problems.
- Mathematically yes, but with significant fit risk. The further you scale from the original, the more proportional distortions accumulate. A pattern designed for extra-small typically has shoulder width, armscye (armhole) depth, and torso length proportioned for that size — simply scaling up produces an armhole that might be geometrically correct in measurement but wrong in shape for a larger body. For large size changes (more than 2–3 sizes), consider consulting a sloper (basic block) for your actual measurements and redrafting the pattern pieces from scratch. Or start with a pattern in a size closer to your target and make fitting adjustments.