Sewing Pattern Scale Calculator
Scale a sewing pattern up or down.
Enter original and desired measurements to get the exact scale factor and grid instructions.
Why Sewing Patterns Need Scaling
Commercial sewing patterns are printed in standard sizes, but bodies do not come in standard sizes. Pattern scaling allows you to enlarge or reduce a pattern to match a specific measurement — a chest, waist, hip, sleeve length, or any key dimension. This is more precise than simply buying the next size up, because scaling preserves the shape and proportions of the original design.
How Scale Factor Works
The scale factor is simply the ratio of the desired measurement to the original measurement. If the original pattern chest measurement is 36 inches and you need 40 inches, the scale factor is 40 ÷ 36 = 1.111, or 111.1%. Every line on the pattern — including seam allowances, dart widths, and pocket placements — must be multiplied by this factor.
Scaling on a Grid
Most patterns include a grid square that represents a real-world size (typically 1 inch or 2 cm). When photocopying or projector-printing a pattern, change the scale percentage on the printer/copier to the calculated factor. Always verify by measuring the printed grid square against a ruler before cutting. If the grid square now measures the correct size, all pattern pieces are correctly scaled.
When to Scale vs. Grade
Scaling uniformly enlarges or reduces the entire pattern in all directions simultaneously. Grading changes only specific measurements (such as widening the hip while keeping the shoulders the same). For a simple size change where body proportions are similar to the original, uniform scaling is fast and effective. For complex body shape differences, full grading between sizes is more accurate.
Practical Limits
Scaling works best within a range of about 85–120% of the original. Beyond this range, style lines, pocket positions, and design details can look distorted. Very large scale changes (e.g., scaling a children’s pattern to adult) usually require full redrafting rather than simple scaling. Always make a muslin (toile) test garment from inexpensive fabric before cutting into your fashion fabric.