Perfectly scaled sprite menu in every resolution

I've spent quite a lot of time looking for an answer. Might be a duplicate question, etc. If I'm asking - it's because I need an answer. I'm making a menu using sprites, but I have encountered a scaling problem once the resolution changes. The sprite vertical size/height remains constant, but it gets a bit stretched horizontally. Now, how can I scale the sprites based on the screen resolution so no matter what the resolution is - on the screen they all appear the same shape and size? I'm working with c# and am trying to achieve this with perspective camera, for I will need 3d elements in the menu.