Here’s a helpful tip for Pi Day: On a Windows computer, you can enter the symbol for π by holding down the ALT key, typing 227 using the numeric keypad,1 and then releasing the ALT key.
The mildly geeky amongst us will remember this by noting 22/7 is a common approximation for pi. The more geeky will avoid using this approximation and instead remember enough significant digits2 of pi.
2I find 3.1415926 is adequate significant digits for all my purposes. Or better yet, just use the “pi” button on the calculator.