What is a good file size for spritesheets (mobile)?

I’m just starting with unity and creating my first mobile game. It will be a 2D game for Android an Windows phone 8.1 / universal 8.1.

I have imported some spritesheets with my main characters but I’m not sure at what size I should import them. At First I made them pretty large: 4096x4096, individual sprites are about 250x450 px. Then I set the MaxSize on the sprite in unity to 1024x1024. But then I started to worry about the size of my .apk (for android), so I resized the actual spritesheet down to 1024x1024. This effectively reduced the .apk size as I thought it would, but now my sprites don’t really scale to bigger screens. Is there a way to keep my .apk small and don’t lose the quality of the sprites?

Also, when I replaced the spritesheets in unity, I lost all my animation clips, so I had to recreate them. Is there a way to reuse the existing animation clips with the resized spritesheet?

Ok so a couple things, look into device support for texture sizes, as some older devices wont support 4096 texture sizes, while they are certainly the nicest quality. I would look into the asset bundles for your sprites, and that way you can set images for HD and SD. 2048 is a good max size if you wanted a default, though depending on the platform this could be pretty heavy, so look into the compression types (ETC, PVRTC for Android and IOS respectively). Make sure you keep with the Power of Two sizes, as they will compress properly on Mobile.

Try and avoid using the Limit size though, as its not very good, Create the images yourself at the sizes you want, within an external program so you can ensure that the quality presented is what you’re actually looking for/okay with.

Now if you’re ever planning on actually replacing sprite sheets, Make sure you have your Meta files not hidden within the project, and replace it within the directory directly and not within the project window, as generally it will overwrite your current meta file.

Let me know if you have other questions, or concerns though. Hope that helps!