Windows: press Alt + 0176 on the numeric keypad
Mac: press Option + Shift + 8
iPhone/iPad: press and hold 0, then select °
Android: press and hold 0, then select °
Copy and paste this symbol: °
In HTML: use ° or °
In Microsoft Word: type 00B0 then press Alt + X
In Google Docs: Insert > Special characters > search for degree symbol