Sewing Pattern Scale Calculator
Lengths scale with the percentage, but fabric use scales with its square. A 20 cm line at 120% becomes 24 cm while the area of the same piece becomes 144% — which is why a slightly enlarged pattern runs out of fabric. The printer zoom is that same 120%.
Your numbers
Scaled measurement
24cm
Formula
Scaled measurement = Finished length × Scale ÷ 100
Turn off "fit to page" when printing and type the scale in yourself, then measure the test square printed on the pattern before cutting anything. Seam allowances stay at their original width instead of being scaled up.
What to enter
| Input | Default | Accepted range |
|---|---|---|
| Finished length (cm)The length when finished. | 20 | 0.1 and up |
| Scale (%)How far to scale a pattern; 100% is the original. | 120 | 10 ~ 400 |
Step by step
Quick reference table
Results when only Finished length (cm) changes and everything else stays put.
| Finished length (cm) | Scaled measurement (cm) |
|---|---|
| 10 | 12 |
| 15 | 18 |
| 20 | 24 |
| 30 | 36 |
| 40 | 48 |
What each result means
| Result | At default values |
|---|---|
| Scaled measurement (cm)The measurement after scaling. | 24 |
Common mistakes
Turn off "fit to page" when printing and type the scale in yourself, then measure the test square printed on the pattern before cutting anything. Seam allowances stay at their original width instead of being scaled up.
Glossary
- Finished length
- The length when finished.
- Scale
- How far to scale a pattern; 100% is the original.
- Scaled measurement
- The measurement after scaling.
Frequently asked questions
Q. How is Sewing Pattern Scale Calculator calculated?
Scaled measurement = Finished length × Scale ÷ 100 — Lengths scale with the percentage, but fabric use scales with its square. A 20 cm line at 120% becomes 24 cm while the area of the same piece becomes 144% — which is why a slightly enlarged pattern runs out of fabric. The printer zoom is that same 120%.
Q. Can you walk through an example?
With Finished length 20cm, Scale 120%, the answer is Scaled measurement 24cm.
Q. What do I need to enter?
Enter Finished length, Scale. The result recalculates as you type, and an empty box counts as zero.
Q. How much does the answer move if I change a number?
Changing only Finished length (cm) moves the answer to Finished length (cm) 10 → Scaled measurement (cm) 12 and Finished length (cm) 40 → Scaled measurement (cm) 48. The table below lays out five steps.
Q. How are the numbers rounded?
Money is shown to the nearest whole unit, percentages to one decimal place and everything else to two. What you see is rounded; the calculation itself carries the unrounded value forward.
Q. Anything to watch out for?
Turn off "fit to page" when printing and type the scale in yourself, then measure the test square printed on the pattern before cutting anything. Seam allowances stay at their original width instead of being scaled up.
Related calculators
Materials differ in density and absorption. If your label states a figure, use it — the defaults here are only common values.