do the math! work it out for yourself (used to suggest that the conclusion to be drawn about something is obvious). North American informal

☞ Math is the American abbreviation of mathematics. When the phrase is used in British English, it is usually as do the maths.

2004BBC News: Business I was faced with the choice of either topping up by using paid holiday or a vast reduction in earnings and a financial struggle when I least need it. You do the maths!