freesewing/markdown/dev/tutorials/pattern-design/adding-measurements/en.md

---
title: Adding measurements
order: 130
---

FreeSewing is all about _made-to-measure_ sewing patterns;
we are going to draft our pattern according to the measurements provided to us.

Which begs the question, which measurements?

It is you, as the pattern designer, who decides which measurements are used
to draft your pattern. For our bib, the only measurement we need is the
_head circumference_.

So let's add it as a required measurement.

## Adding required measurements

In our `bib.mjs` file, on the `bib` object, we'll add a new key called
`measurements` that will hold a list (an array) of all required measurements
for this part.

We are going to use *the official name* of the measurement. For head
circumference, that name is `head`. 

```design/src/bib.mjs
function draftBib({ part }) {

  return part
}

export const bib = {
  name: 'tutorial.bib',
  draft: draftBib,
  // Add this line:
  measurements: ['head'],
}
```

Now everybody knows this part requires the `head` measurement.

This change will also get picked up by the development environment, and you'll now see this screen:

![This screen tells you you are missing some required measurements](./required-measurements.png)

Since it's just one measurement, let's simply enter a value by hand.
For example `38` as 38cm is a realistic head circumference measurement for a baby.

Enter `38` in the box, and click on **Draft Design** in the sidebar under the **View** heading.
This brings you back to our work in progress:


## Notes

### Why using standard measurements names matters

In principle, you can use any name you want for your measurements.
Our core library really doesn't care.

However, if everybody uses their own (names for) measurements, then people
aren't able to re-use their measurements across designs.

So if you have any intention at all to play nice with the FreeSewing ecosystem,
please make sure to re-use the names of existing measurements, rather than
invent your own.

See our [best practices](/guides/best-practices/reuse-measurements) on this
topic for details.