Pattern Size Scaler
Enter your original and new key measurements to get the scale factor and rescaled dimensions.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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This tool rescales all your pattern measurements proportionally when you need to make a pattern larger or smaller. It works for sewing patterns, crochet, embroidery templates, and any other craft that uses measured dimensions.
- Enter your key measurement. This is the measurement that defines the size change — typically the bust, waist, or chest circumference from the original pattern size you have and the size you want to make.
- Enter all other measurements to scale. Type in the other dimensions from your pattern, separated by commas or on separate lines. These might be seam lengths, dart widths, sleeve lengths, or any other dimension that needs to change proportionally.
- Read the scale factor and scaled measurements. The scale factor is the ratio of new to original. All your listed measurements are multiplied by this factor.
Note: Pattern grading is not always purely proportional. Body proportions do not scale linearly with size, so professional pattern grading uses different rules for different areas. This calculator gives a proportional starting point that works well for most casual scaling needs.
About the Pattern Size Scaler
The scale factor is simply the new measurement divided by the original measurement. All other measurements multiply by this ratio. For example, scaling from a 36" chest to a 40" chest gives a scale factor of 40/36 = 1.111. A 12" sleeve length becomes 12 × 1.111 = 13.33". This method is called uniform scaling and preserves all proportions. For enlarging patterns printed on paper, you can use the same factor when setting your printer's zoom percentage (convert the decimal factor to a percentage, e.g. 1.111 = 111%).
Frequently Asked Questions
How do I scale a sewing pattern up by one size?
Find the key measurement for your current size and the next size up in the pattern's size chart (usually the bust or chest circumference). Enter the original measurement and the new measurement into this calculator. The scale factor and all rescaled dimensions will appear instantly. For sewing patterns, it is usually better to grade between sizes using the pattern's grading lines rather than scaling uniformly, but uniform scaling works well for simple shapes.
Can I use this to enlarge a pattern that was printed too small?
Yes. Measure a known dimension on the printed pattern (like a 1" test square if the pattern includes one), then enter the printed size and the correct size. The scale factor tells you the percentage to use when reprinting or photocopying. For example, if a 1" square on the pattern measures 0.8", enter 0.8 as original and 1.0 as new. The scale factor of 1.25 means you need to print at 125% scale.
Does scaling a pattern proportionally always give the right fit?
Not always. Human body proportions are not linear — a size 14 is not simply a scaled-up size 8. For simple shapes like pouches, bags, or decorative items, uniform scaling works perfectly. For fitted garments, especially around the shoulder, armhole, and crotch areas, you may need to adjust specific measurements by hand after scaling. Use this calculator as a starting point and do a muslin fitting to check before cutting into your final fabric.
How do I scale a knitting or crochet pattern for a different size?
For knitting and crochet, use your gauge (stitches per inch) alongside the scale factor. Find the target finished width, multiply by your gauge to get the new stitch count, and adjust for your pattern's required stitch multiple. The pattern scaler helps with the dimensional measurements (sleeve length, body length, neckline width) while the gauge calculator handles the stitch counts. Use both tools together for complete pattern conversion.