How the pan size converter works
What matters is the area of the pan, because the batter should end up the same depth. A 9-inch round pan has about 64 square inches, a 9×13-inch pan has 117. Divide one by the other and you get the factor to multiply every ingredient by.
Baking time
If the batter is the same depth, the baking time stays close to the original. A deeper layer needs a lower temperature and more time, a thinner one bakes faster. Start checking 10 minutes early with a skewer.
Common swaps
- Two 8-inch rounds (100 sq in) ≈ one 9×9-inch square (81 sq in) plus a few cupcakes.
- One 9×13-inch pan (117 sq in) ≈ two 9-inch rounds (127 sq in).
- A 20 cm round (314 cm²) ≈ an 18 cm square (324 cm²).