You will not need to do any conversion, as long the developer is working in `pt` on iOS, `dp` on Android, and `px` in CSS. This is why the units don't change in design specs If the developer is using any other unit, such as native `px` on iOS or Android, then they will need to make the conversion, however this conversion depends on the pixel density of the device the application is running on. The formula you have above is correct for Android (see Supporting Multiple Screens | Android Developers ) however it is up to your developer to make this calculation based on the current device's pixel density. If you, as the designer, make this calculation in advance then the measurements will be incorrect when the application is viewed on, for example, a mdpi then an xxhdpi device. I hope this helps!
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