Cake Pan Size Converter
Recipe calls for two 9-inch rounds but you have a 9×13? Pick both pans to get the exact multiplier for your ingredients, and what it means for bake time.
How the conversion works
Most cake pans are about 2 inches deep, so how much batter a pan holds comes down to its area. To keep your cake the same thickness as the original, scale the recipe by the ratio of the two areas:
- Round pan: π × radius² (a 9-inch round is 3.1416 × 4.5 × 4.5 ≈ 63.6 sq in)
- Square pan: side × side (an 8-inch square is 64 sq in)
- Rectangular pan: length × width (a 9×13 is 117 sq in)
Multiplier = your pan's area ÷ the recipe pan's area. Two 9-inch rounds total 127 sq in, and a 9×13 is 117 sq in, so 117 ÷ 127 = 0.92. A two-layer cake recipe fills a 9×13 almost exactly, and the sheet cake comes out just slightly thinner than each layer would have been.
Cake pan area chart
| Pan | Area (sq in) | Area (cm²) | vs. one 9" round |
|---|---|---|---|
| 6-inch round | 28.3 | 182 | 0.44× |
| 8-inch round | 50.3 | 324 | 0.79× |
| 9-inch round | 63.6 | 410 | 1.00× |
| 10-inch round | 78.5 | 507 | 1.23× |
| 12-inch round | 113.1 | 730 | 1.78× |
| 8-inch square | 64 | 413 | 1.01× |
| 9-inch square | 81 | 523 | 1.27× |
| 10-inch square | 100 | 645 | 1.57× |
| 7×11-inch rectangle | 77 | 497 | 1.21× |
| 9×13-inch rectangle | 117 | 755 | 1.84× |
| 10×15-inch jelly roll* | 150 | 968 | 2.36× |
| 13×18-inch half sheet* | 234 | 1,510 | 3.68× |
| 9×5-inch loaf pan† | 45 | 290 | 0.71× |
| 8½×4½-inch loaf pan† | 38.3 | 247 | 0.60× |
* Jelly roll and sheet pans are only about 1 inch deep, so fill them with about half the batter their area suggests, or expect a thick cake that needs more time. † Loaf pans are deeper (2½–3 inches), so they hold more batter than their area suggests and need longer, slower baking.
One handy takeaway: an 8-inch square and a 9-inch round are practically interchangeable (64 vs 63.6 sq in).
Adjusting bake time and temperature
- You scaled the recipe (same depth): bake time stays close to the original. Large pans can need a few extra minutes because the center is farther from the hot edges, so start checking at the original time.
- Batter is shallower than the original: it bakes faster. Start checking about a third sooner.
- Batter is deeper than the original: lower the oven by 25 °F (about 15 °C) and bake longer, so the center sets before the edges dry out. Never fill a cake pan more than about two-thirds full.
- Very large pans (12-inch rounds and up) bake more evenly with a heating core or an upside-down flower nail in the center.
- Test for doneness with a toothpick inserted in the center. It should come out with a few moist crumbs but no wet batter. Most butter cakes read about 200–210 °F in the center when done.
Bundt pans, cupcakes and odd shapes
Bundt, tube and novelty pans are best compared by volume rather than area. Fill the pan with water one cup at a time to find its capacity, do the same with the recipe's pan (or look up its capacity), and scale by the ratio. Fill any pan about two-thirds full. For cupcakes, a recipe for two 9-inch layers typically makes about 24 standard cupcakes. Bake them at the same temperature for roughly 18–22 minutes.
Frequently asked questions
Can I bake a 9-inch round recipe in an 8-inch square pan?
Yes. Their areas are almost identical (63.6 vs 64 sq in), so use the recipe as written and bake for about the same time.
How do I turn a layer cake into a 9×13 sheet cake?
A recipe for two 9-inch rounds fits a 9×13 almost exactly (multiplier 0.92), so use the full recipe. The single sheet is a bit deeper than each layer was, so expect about 5–10 extra minutes and check with a toothpick. A recipe for two 8-inch rounds (100 sq in total) should be scaled up by about 1.15.
Does pan material change anything?
Dark metal pans absorb more heat and brown edges faster, and glass holds heat longer. For either, many bakers lower the oven by 25 °F. Light-colored aluminum pans bake the most evenly.
What if my pan has sloped sides?
Measure across the top inside edge for diameter or length. Sloped pans hold slightly less than their top measurement suggests, so round the multiplier down a little.