Excel glossary What is a Formula in Excel A formula is a type of equation. An equation says that two things are equal, that is why in Excel a formula always starts with ‘=’. A formula shows the correlation between two or more variables. A Formula in a Spreadsheet A formula in a spreadsheet can be built up from the following components: Constants Values Functions Operator signs Cell references Excel Functions A function in Excel is also a type of formula, but it is preset to help perform mathematical, statistical and logical operations. A formula can contain one or more functions.