Baking Pan Size Conversions

To swap one baking pan for another, compare their floor area rather than their width. The batter depth, and so the bake time and rise, follows the area of the pan. The baking pan converter calculates the area of each pan and the ratio between them, so you know how to adjust the recipe.

Work in area, not width

A pan that is one inch wider holds a lot more than the inch suggests, because area grows with the square of the size. The formulas are simple:

Round: pi times the radius squared. A 9-inch round has a radius of 4.5 inches, so the area is about 63.6 square inches.
Square and rectangle: length times width. An 8-inch square is 64 square inches; a 9 by 13 inch pan is 117 square inches.

Comparing those areas tells you whether two pans are interchangeable and how much to scale a recipe if they are not.

Common pan areas

Pan	Floor area (sq in)
8-inch round	50
9-inch round	64
8-inch square	64
9-inch square	81
9 x 5 loaf	45
9 x 13 rectangle	117

From this you can see the classic swap: an 8-inch square and a 9-inch round are both about 64 square inches, so a recipe for one fits the other with no change.

Adjusting the recipe

When the areas differ, scale the recipe by the area ratio. If the new pan is 25 percent larger, increase the batter by about 25 percent to keep the same depth, or accept a thinner bake that cooks faster. If the new pan is smaller, scale down or expect a deeper bake that needs longer. The recipe scaler handles the ingredient maths once you know the ratio.

Watch the bake, not the clock

Changing pans changes depth, and depth changes timing. The oven temperature usually stays the same, but a shallow bake in a wide pan can finish well before the recipe time, while a deep bake in a narrow pan runs over. Start checking based on which way the depth moved, and judge by a toothpick or the spring of the surface rather than the timer.

Convert your pans

Pick the pan your recipe wants and the pan you have in the baking pan converter to see the area ratio and a plain-language note on what to do.

Frequently asked questions

How do I substitute one cake pan for another?

Compare the floor area of the two pans, not their widths. A round pan area is pi times the radius squared, and a square or rectangle is length times width. If the new pan has more area, the batter sits shallower and bakes faster; less area means deeper and slower. The pan converter gives the exact area ratio and what to do about it.

Is an 8-inch square the same as a 9-inch round?

They are very close. An 8-inch square is 64 square inches and a 9-inch round is about 63.6 square inches, so you can usually swap them with no change to the recipe. This is one of the most useful pan swaps to know, and the converter confirms it for any pair you choose.

Do I need to change the bake time when I change pans?

Often yes. A shallower batter in a larger pan cooks faster, and a deeper batter in a smaller pan cooks slower. The temperature usually stays the same. Start checking earlier or later than the recipe says depending on which way the depth changed, and use the toothpick test rather than the clock.