An array formula is a formula that can perform multiple calculations on one or more of the items in an array. We can think of an array as a row of values, a column of values, or a combination of rows and columns of values. Array formulas can return either multiple results or a single result. For example, we can create an array formula in a range of cells and use the array formula to calculate a column or row of subtotals. We can also place an array formula in a single cell and calculate a single amount. An array formula that includes multiple cells is called a multi-cell formula, and an array formula in a single cell is called a single-cell formula.