4:5 is an exact fit.
If you use the Photos app on your phone to crop the pic, the 4:5 option won't show until you select a portrait-like "taller than wide" area -- it'll be 5:4 instead. You don't have to crop it once and then crop again -- just drag the corners of the crop area so it becomes tall, then tap the aspect ratio presets button.
I'll upload screenshots in a minute -