Cake pan converter

How do I convert a recipe to a different pan size?

Compare the areas of the pan bottoms and scale the recipe by the ratio. A 9-inch round is 63.6 in²; a 9 × 13 pan is 117 in², so it needs 117 ÷ 63.6 = 1.84 times the batter.

Can I bake a 9-inch round cake in an 8-inch square pan?

Yes — an 8 × 8 square is 64 in², almost exactly a 9-inch round (63.6 in²), so the same batter fits at the same depth.

Will a 9 × 13 recipe fill two 9-inch rounds?

Just about: two 9-inch rounds are 127.2 in² against 117 in², so the layers come out about 8% thinner. Check them a few minutes early.

How do I work out the area of a round pan?

π × radius²: an 8-inch round is 3.1416 × 4² = 50.3 in², a 10-inch round 78.5 in². A 10-inch round holds over 1.5 times an 8-inch.

Does the baking time change?

At the same batter depth, only a little. Deeper batter needs a lower temperature and more time, shallower batter less time — start checking early with a toothpick.

Does the pan depth matter?

Yes. The converter compares the area of the pan bottoms, which assumes the batter ends up about as deep as in the original recipe. A pan that is much deeper or shallower than the original changes the baking time and may overflow or give a thin cake. Match the batter depth, not only the area.

How do I measure a pan?

Measure across the inside of the pan at the top, from one inner edge to the other, for the width, length or diameter. Pans are often labeled by outside size, which can be slightly larger than the inside.

What if the new pan holds less batter than the recipe makes?

Scale the recipe down by the area ratio, or use the extra batter in a second small pan or in muffin cups, which bake faster than a cake. Do not fill the pan higher than the original depth, because the cake may rise over the edge.

How the calculation works

The area of a round pan is π × diameter² ÷ 4, a square pan is the side squared, and a rectangular pan is length times width, all measured on the inside in inches. The converter adds up the areas of all the pans in each set and divides the new total by the original. A ratio of 1.5 means the new pans hold about 1.5 times as much batter at the same depth, so the recipe is multiplied by 1.5. A ratio below 1 means you scale down.

Worked example

A recipe is written for a 9 × 13-inch pan, whose bottom area is 117 square inches. Here is how some other pans compare: two 8-inch round pans (100.5 in², 0.86 times the original); one 10-inch round pan (78.5 in², 0.67 times the original); one 9-inch square pan (81 in², 0.69 times the original); one 8 × 8-inch square pan (64 in², 0.55 times the original). A ratio below 1 means the new pans hold less batter than the original, so scale the recipe down by that ratio: for the single 8 × 8 pan, use about 55% of every ingredient. Two 8-inch rounds come closest at 0.86, and the layers would be thicker if you used the whole recipe in them.

Common mistakes

• Comparing pan names instead of areas. An 8-inch square pan (64 square inches) is not the same as an 8-inch round (50.3 square inches).
• Forgetting that scaling affects the ingredients unevenly. Scaling by an odd ratio can leave you with a fraction of an egg. Beat an egg and use the corresponding part by weight or volume.
• Keeping the same time. A shallower layer bakes faster and a deeper one slower. Start checking early and use a toothpick.

Sources and related calculators

Method: plane geometry for the pan areas (area of a circle, square and rectangle), with batter volume assumed proportional to bottom area at equal depth. Related: recipe scaler, recipe resizer and area calculator.