Pan Size Conversion Calculator

Area, not diameter or side length, is what actually matters

A recipe fills a pan to a certain depth, so what needs to match (or be scaled to) is surface area, not any single dimension — a 9" round pan (about 63.6 in²) and an 8"×8" square pan (64 in²) are almost exactly the same area, which is why they're commonly treated as interchangeable, even though "9" and "8" look like different numbers.

Scale factor tells you how much to adjust the recipe

Scale factor = new pan area ÷ original pan area. A factor above 1 means the new pan is bigger, so scale the recipe up by that factor (see the Recipe Scaling Calculator); a factor below 1 means the new pan is smaller, so scale down, or expect a thicker result if you don't adjust the recipe at all.

Bake time still needs to be checked, not scaled the same way

A wider, shallower pan generally bakes faster than a smaller, deeper one holding the same batter volume, since heat reaches the center faster through a thinner layer — don't assume bake time scales with the same factor as the ingredients. Start checking doneness earlier than the original recipe's time in a wider pan, and later in a deeper one.