In what screen sizes to build an application on xamarin?

Question

Mobile development

For the first time I come across both Xamarin and mobile development.
I shoveled through the documentation and articles, and here's what I got:
dp == width_in_px * 160 / dpi
There is the concept of Screen Density. For example xhdpi where 1dp == 2px
I installed Xamarin Live Player. I take my iPad Air2.
I find out on google that dpi == 264px per inch. Resolution is 2048x1536px. I paste it into the formula and calculate:
width_in_dp == 2048 * 160 / 264. This equals 1241.
I set the AbsoluteLayout Label with a point of 0 0 and a width of 1241px. I get a wider element.
I find device metrics from google, they indicate Screen Density xhdpi for ipad. Taking into account the new information, I divide and get 1024dp. And it fits. https://material.io/devices/
And here is my question:
Why is the first formula wrong and how are Xamarin applications designed in terms of size? To correctly display on devices of various sizes?

Answer 1

The sizes you use in Xamarin.Forms are values ​​that are set for platforms to be equal to their size measurement types. For UWP it's Effective pixels, for iOS it's Points, and for Android it's Density-independent pixels.
A couple of links on this topic:
Working with sizes
Image sizes
How to find out the size in pixels on the platform, for cont...