Windows: hold Alt and type 0176 on the numeric keypad
Mac: press Option + Shift + 8
Chromebook: press Ctrl + Shift + U, type 00B0, then press Enter
iPhone or iPad: press and hold 0, then select °
Android: press and hold 0, then select °
In Microsoft Word: type 00B0 and press Alt + X
In HTML: use ° or °