How do I write a formula with more than one IF condition?

Each IF checks one condition and gives two outcomes: what to return if it is true, and what to return if it is false. Nesting means the "false" outcome of one IF is itself another IF, so you keep testing conditions until one matches. The example above assigns a letter grade by checking, in order, whether a score is 90+, then 80+, then 70+, and otherwise falling through to the last value.

The main risk with nested IFs is readability: past three or four levels deep, a formula becomes hard to audit and easy to break when someone edits it later. Where your spreadsheet program supports it, IFS(condition1, result1, condition2, result2, ...) reads the same conditions in a flatter, more readable list.