Pan Substitution Calculator

Compare the surface area of the two pans, not their named size. A recipe fills a pan to a certain depth, and depth depends on area. Work out the area of the pan the recipe calls for and the area of the pan you have, then divide the new area by the original. That ratio is how much to scale the recipe to fill the new pan to the same depth — this calculator does the area math for round, square, and rectangular pans.

Almost exactly. A 9-inch round pan has an area of about 63.6 square inches, and an 8-inch square pan is 64 square inches — a difference well under 1%. They are interchangeable for most recipes with no change at all. That is a good example of why area matters more than the pan’s name: the round and the square sound different but hold the same amount.

It changes with the batter depth, not the pan name. If you keep the same recipe and move to a larger pan, the batter spreads thinner and bakes faster — start checking 5 to 10 minutes early. A smaller pan makes a deeper batter that bakes slower, and very deep pans can brown on top before the centre is set, so lowering the oven by about 25°F helps. The calculator flags which way your swap goes.

The area of a round pan is pi times the radius squared, where the radius is half the diameter. For a 9-inch round pan the radius is 4.5 inches, so the area is 3.14159 × 4.5 × 4.5, which is about 63.6 square inches. A square or rectangular pan is simpler — just multiply the two side lengths. The calculator handles all three shapes for you.

Yes. The scale factor is a ratio of two areas, so the unit cancels out — as long as you measure both pans in the same unit, the factor is the same whether you use inches or centimetres. The common-pan presets are in inches because that is how North American bakeware is sized, but you can type centimetre dimensions directly and the result still holds.

This calculator compares the floor area of the pans, which is what governs how a fixed amount of batter spreads out. It assumes both pans are deep enough to hold the batter. If your new pan is unusually shallow, scale the recipe down a little so the batter does not overflow, and remember that cake and quick-bread batters typically rise as they bake.