The recipe says 9 inch round pans, and the only pan you own is an 8 inch square. Do you use the same batter? Do you need more or less? Pour in all of it and the cake overflows, pour in half and it comes out as a thin pancake.
The answer is a ratio. Compare the size of the two pans and scale the recipe by that number. This cake pan converter measures the area, or the volume if the pans differ in depth, and tells you the multiplier.
How to use the Cake Pan Converter#
- Choose your unit. Pick inches or centimetres.
- Describe the recipe pan. Choose its shape and enter the diameter, or the length and width.
- Describe your pan. Do the same for the pan you plan to use.
- Check the depth. Leave the box ticked if both pans are about the same depth. Untick it to enter the depths.
- Scale an amount. Type an ingredient quantity to see the scaled version, or read the ratio directly.
How the cake pan converter works#
A cake batter spreads across the bottom of the pan and rises to a certain height. If two pans have the same depth, the amount of batter you need is proportional to the floor area of each pan. A round pan has an area of pi times the radius squared, a square pan has an area of its side squared, and a rectangle has an area of length times width. Divide the area of your pan by the area of the recipe pan and you have the scaling factor.
If the depths differ, use volume instead. That is the area multiplied by the depth. One US cup is 14.4375 cubic inches, so the converter also shows the capacity of each pan in cups.
Common pan areas#
| Pan | Area (sq in) | Area (sq cm) |
|---|---|---|
| 6 inch round | 28.3 | 182 |
| 8 inch round | 50.3 | 324 |
| 9 inch round | 63.6 | 410 |
| 10 inch round | 78.5 | 507 |
| 8 inch square | 64.0 | 413 |
| 9 inch square | 81.0 | 523 |
| 9 by 13 inch | 117.0 | 755 |
This table shows why some swaps work. A 9 inch round pan has an area of 63.6 square inches and an 8 inch square pan has 64, so the two are nearly interchangeable. A 9 by 13 inch pan is 117 square inches, a little less than two 9 inch rounds at 127.
A worked example#
The recipe is for a 9 inch round pan, and you want to bake in a 7 by 11 inch rectangle. The round pan has an area of 63.6 square inches. The rectangle has 77. The ratio is 77 divided by 63.6, which is 1.21, so you scale up by about 21 percent. A recipe that needs 2 cups of flour would need about 2.4 cups, and three eggs would become about 3.6, which in practice means three large eggs and a splash of a fourth beaten egg.
Baking time and temperature#
There is no exact formula for baking time. If you scale the batter to keep the same depth, the cake bakes for roughly the same time,. If the batter is deeper than the recipe intended, lower the oven by about 25 degrees Fahrenheit (15 Celsius) and bake longer, so the outside does not set before the middle has cooked. Always test with a skewer, and look for a clean one or a few dry crumbs.
How full should the pan be?#
Fill a cake pan between one half and two thirds full. Fuller than that and the batter rises over the top. Much less and the cake bakes thin and dry. The capacity figure in the converter is a quick way to check. A 9 by 13 by 2 inch pan holds about 16 cups, so it should take about 8 to 11 cups of batter, depending on how much your recipe rises.
Loaf, bundt and cupcake pans#
The ratio method works for any pan you can measure, but the shapes get harder to compare. A standard 9 by 5 inch loaf pan that is 3 inches deep holds about 135 cubic inches, or 9.4 cups, so it is close to the capacity of an 8 inch square pan, which holds about 8.9 cups at 2 inches deep. Bundt and tube pans are sold by capacity, such as a 10 or 12 cup pan, and the easiest way to compare them with anything else is to fill the pan with water, one cup at a time, and count the cups. Use the capacity in cups with the depth box unticked to get a ratio. For cupcakes, fill each liner about two thirds full, and use the total batter volume of the recipe to estimate how many a larger recipe will make.
Frequently asked questions#
Yes. Compare the areas. A 9 inch round pan is almost the same as an 8 inch square pan, so you can use the same batter.
Divide the area of the 10 inch pan, 78.5 square inches, by the area of the 9 inch pan, 63.6. That is 1.23, so scale the recipe up by about a quarter.
Not if you scale the batter to keep the same depth. A deeper batter does need longer, at a slightly lower temperature.
Untick the same depth box and enter both depths. The converter then uses volume instead of area.
Multiply the number of eggs by the ratio and round to the nearest half. For a half egg, beat one egg and use about one and a half tablespoons of it.
Between one half and two thirds full, so the cake has room to rise.
Sources and further reading#
- Omni Calculator: Cake Pan Converter. Cross-check of the area and volume method.
- NIST Special Publication 811: Guide for the Use of the International System of Units. Exact definitions of the inch, pound, ounce and the units derived from them.
- Wikipedia: Cup (unit). The US cup in cubic inches and millilitres.