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# CGDisplayScreenSize(_:)

Returns the width and height of a display in millimeters.

```
func CGDisplayScreenSize(_ display: CGDirectDisplayID) -> CGSize
```

## Parameters

`display`

The identifier of the display to be accessed.

## Return Value

The size of the specified display in millimeters, or 0 if the display is not valid.

## Discussion

If Extended Display Identification Data (EDID) for the display device is not available, the size is estimated based on the device width and height in pixels from [`CGDisplayBounds(_:)`](/documentation/CoreGraphics/CGDisplayBounds(_:)), with an assumed resolution of 2.835 pixels/mm or 72 dpi, a reasonable guess for displays predating EDID support.

---

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