Pixel to MM equation?

Question

Is there a reliable equation to work out pixel size to MM? Or is that not possible cross device?

We are working with a bespoke system that delivers content to many

Answer 1

tl;dr: If you don't know the DPI of the device, you won't be able to deduce how big the pixel is in the real-world.

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Pixels on their own are not real-world units of measurement.

They can become a real-world measurement if you take into account the DPI value of the device that displays them.

The formula is:

• mm = ( pixels * 25.4 ) / DPI

So 8 pixels viewed on a 96-DPI screen setting:

• ( 8 * 25.4 ) / 96 = 2.116mm

All this assuming the device is not scaled/zoomed.

Answer 2

You cannot reliably calculate this since there is no way to detect physical screen size.

Answer 3

You would need to know the DPI of the device and if the display is scaled or not. That would mean that you would have to have a database of the physical screen dimensions and screen resolutions of each device.