Base areas of common US pans, and the factor to scale a 9x13 recipe into each. Scaling by area keeps the batter as deep as the recipe intended.
How to use the chart
To move a recipe to another pan, divide the new pan’s area by the old one’s and multiply every ingredient by the result. The last column gives that factor for a 9x13 recipe. Scaling by area keeps the batter at the same depth, so the baking time stays close; start checking a little early.
A round pan holds less than a square pan of the same width: the 8" round pan is 50.3 sq in and the 8x8" square pan 64 sq in. That is also why a recipe for one 9" round pan (63.6 sq in) fits the 8x8" square pan almost exactly.
Measure a pan across the top, from inside edge to inside edge, not across the bottom or the outside: that is the size recipes and labels give. Pans with sloped sides are smaller at the bottom than the size on the label.
Frequently asked questions
Which pans are the same size as a 9x13" pan?
The closest are two 9" round pans (127.2 sq in) or two 8x8" square pans (128 sq in), against its 117 sq in.
Is an 8x8" square pan the same as a 9" round pan?
Almost: the 8x8" square pan is 64 sq in and the 9" round pan 63.6 sq in, 0.6 % apart, so the same recipe fits both.
How much bigger is a 9x13" pan than an 8x8" square pan?
The 9x13" pan is 117 sq in and the 8x8" square pan 64 sq in, so multiply an 8x8" square recipe by 1.83 (about 1 3/4 ×) to fill a 9x13" pan.