> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Display map scale
This example uses [`Map.addControl`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addcontrol) to add a [`ScaleControl`](https://docs.mapbox.com/mapbox-gl-js/ja/api/markers/#scalecontrol) to the map, displaying the real-world distance represented by the map's current zoom level.
When instantiating `ScaleControl`, there are two optional parameters:
- `maxWidth`: sets the maximum width in pixels to use to display the scale bar.
- `unit`: sets the unit of measurement. Options include - `imperial`, `metric` and `nautical`.
> Example code:
**JavaScript**
```html
Display map scale
```
**React**
```jsx
import React, { useEffect, useRef } from 'react';
import * as mapboxgl from 'mapbox-gl/esm';
import 'mapbox-gl/dist/mapbox-gl.css';
const MapboxExample = () => {
const mapContainerRef = useRef();
const mapRef = useRef();
useEffect(() => {
mapRef.current = new mapboxgl.Map({
// TO MAKE THE MAP APPEAR YOU MUST
// ADD YOUR ACCESS TOKEN FROM
// https://account.mapbox.com
accessToken: 'YOUR_MAPBOX_ACCESS_TOKEN',
container: mapContainerRef.current,
style: 'mapbox://styles/mapbox/standard',
center: [-74.5, 40],
zoom: 9
});
// Creates a new scale control to measure the map
const scale = new mapboxgl.ScaleControl({
maxWidth: 120, // the max pixel width of the scale bar to be rendered on the map (default is 100 pixels)
unit: 'imperial' // The type of measurement displayed, options are: 'imperial', 'metric', 'nautical' (default it metric)
});
mapRef.current.addControl(scale);
return () => {
mapRef.current.remove();
};
}, []);
return ;
};
export default MapboxExample;
```