Textures - Power of 2 sizes

If your textures are for 3D models and meshes (not sprites or GUI elements), then make their dimensions power-2 size for best results. The textures needn't be square (equal in width and height), but each dimension should be from a range of power-2 sizes--though some target platforms and situations make this a requirement. Valid sizes include 32, 64, 128, 256, 512, 1024, 2048, 4096, and 8192. Sizing textures to a power-2 dimension helps Unity scale textures up and down as well as copy pixels between textures as needed, across the widest range of graphical hardware:

When creating textures, it's always best to design for the largest possible power-2 size you'll need (as opposed to the largest possible size allowed), and then to downscale wherever appropriate to smaller power-2 sizes for older hardware and weaker systems, such as mobile devices. For each imported texture, you can use the Unity platform tabs from the Inspector object to specify an appropriate maximum size for each texture on a specific platform: one for desktop systems, one for Android, one for iOS, and so on. This caps the maximum size allowed for the selected target on a per-platform basis. This value should be the smallest size that is compatible with your artistic intentions and intended quality: