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When the recipe’s tin is not your tin
Cake recipes are written for one pan size, and home kitchens rarely own exactly that pan. Pour the batter into something larger and you get a thin cake that dries out; squeeze it into something smaller and it domes, cracks or spills over. This converter compares the two pans and tells you how much to scale the recipe so the batter sits at the same depth.
It works for round, square and rectangular pans in centimetres or inches, and it is handy for layer cakes, sheet cakes, brownies and cheesecakes alike.
Why depth is what matters
Heat moves into a cake from the edges and the bottom. A cake of the same depth, in any shape, bakes in roughly the same time because the heat has the same distance to travel to the middle. So the reliable way to change pans is to keep the batter depth constant, and that means scaling the recipe by the ratio of the pan areas.
Areas grow faster than people expect. A 9 in round is only an inch wider than an 8 in round, but it holds about 27% more batter at the same depth.
Comparing two pans
- Under Original pan, choose the Original pan shape and fill in its size: Original diameter for a round, Original side for a square, or Original length and Original width for a rectangle.
- Under New pan, do the same with New pan shape and its measurements.
- Optionally, enter Batter in the original recipe (optional) to get the new batter weight directly.
The results show Scale the recipe by, the Original pan area and New pan area, and Unscaled batter in the new pan, which tells you how much deeper or shallower the cake would be if you did not scale. A note underneath explains what that means for baking time.
A few pan swaps
A 20 cm round sponge recipe makes 850 g of batter, and you want to bake it in a 23 cm round. The converter shows:
- Scale the recipe by: × 1.32
- Batter for the new pan: 1,124 g
- Original pan area: 314 cm²
- New pan area: 415 cm²
- Unscaled batter in the new pan: × 0.76 as deep, shallower
Multiply every ingredient by 1.32 and the cake will be as deep as the original. Baked unscaled, it would be about three quarters as deep and ready noticeably sooner.
Some swaps need no change at all. A 9 in round (63.6 in²) and an 8 in square (64 in²) are almost identical in area, so the factor is × 1.01 and the converter reports about the same depth.
Going smaller shows the risk. A 9 × 13 in recipe moved to an 8 in square has a factor of × 0.55. Bake the full recipe there and the batter would be × 1.83 as deep, needing far longer and quite possibly overflowing.
Doubling up works the other way: an 8 in round recipe in a 9 × 13 in pan needs × 2.33 the ingredients.
Making the scaled recipe practical
A factor like × 1.32 is awkward to apply by hand, especially to eggs and spoons. The recipe scaler multiplies a whole ingredient list by any factor and turns odd amounts into practical ones, including part eggs. Weights scale most cleanly, so convert cup measures first with the cups to grams converter, and sticks with the butter converter.
Baking tips after a pan change
- Start checking early. Even at the same depth, a much larger cake can take a few extra minutes, and ovens vary.
- Fill pans about halfway to two thirds. That leaves room for the rise in most butter and sponge cakes.
- Dark metal browns faster than light metal or glass. Many bakers lower the oven by around 10 °C (25 °F) for dark pans.
- Use the same pan height. The converter assumes the new pan is at least as deep as the batter needs to be.
- Converting the oven setting too? The oven temperature converter covers fan, convection and gas.
Cake pan questions
Can I bake one layer recipe in two smaller pans?
Yes. Compare the original pan with one of the new pans. The factor is what each new pan needs, so for two pans make the recipe at twice that factor and divide the batter evenly.
What about Bundt or tube pans?
The centre tube removes area in a way this converter does not model. Many bakers compare by volume instead: fill both pans with water and compare the amounts.
Why is my cake still underbaked after scaling?
Usually the oven is running cool, the pan is deeper than the batter, or the batter was colder than the original recipe assumed. An oven thermometer and a skewer test answer most of it.
Does this work for bread in loaf pans?
Loaf dough behaves differently because it rises far more. The loaf pan dough weight calculator is built for tin loaves.