You take 10% of the bill amount, because that’s easy, and you double it. Problem solved.

Back when it was 15% is normal, 10% of the bill, half the 10%, then add those numbers together.

You’re welcome, CNN.

@BoozyBadger I typically just double the tax and round up. Granted Cali so higher taxes ^-^;
@Muzukun I include the tax in my 10% calculation.