Excel array formulas are used extensively in PopTools to return multiple results with a single formula. The result of each array formula will fill more than one cell. PopTools includes menu options to enter many of the array formulas, but others must be entered manually. To enter an array formula you need to know the size of the result. Array formulas can be created in the same way that you create other formulas, except you must press CTRL+SHIFT+ENTER to enter the formula. The image below demonstrates this process, using Excel’s built-in formula for matrix multiplication.