---
title: utils.stretchToScale()
---
The `utils.stretchToScale()` function calculates the scale for a given amount of
stretch.
## Signature
```js
float utils.stretchToScale(float stretch)
```
## Notes
The way people measure stretch intuitively is different from the way we handle stretch in code.
When people say fabric has _25% stretch_ they mean that 10 cm of fabric can
stretch to 12.5 cm.
In code that means we would need to scale non-stretch lengths by 80%
to get the correct lengths to use in patterns with 25% stretch fabric.
Pattern designers need a way to calculate the scaling factor to use for
their pattern part lengths, given a fabric stretch percentage.
This function does that by returning:
```js
1 / (1 + parseFloat(stretch))
```
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