Cake Pan Converter

What this does

So your recipe is written for one cake pan, but you own a different one, and you do not want a cake that overflows or comes out thin and dry. This converter sorts that out. You describe the pan the recipe calls for and the pan you actually have, and it gives you a conversion factor, a single number you multiply every ingredient by so the batter fits your pan properly.

How to use it

1. Under Recipe Pan, pick the shape and enter its dimensions and height.
2. Under My Cake Pan, do the same for the pan you are using.
3. Press Calculate to see both pan volumes and the conversion factor.

Use the same units for both pans, inches for both or centimetres for both. As long as they match, the factor comes out right.

How the conversion works

It comes down to how much batter each pan holds, which is its volume. For a round pan that is:

volume = π × (diameter ÷ 2)^2 × height

And for a square or rectangular pan it is simply:

volume = length × width × height

Then the factor is your pan compared to the recipe pan:

factor = your pan volume ÷ recipe pan volume

Say the recipe calls for an 8 inch round and you have a 9 inch round, both 2 inches tall. The 8 inch holds about 100 cubic inches and the 9 inch about 127, so the factor is roughly 1.27. You would multiply every ingredient by 1.27 to fill the larger pan to the same depth.

Why you cannot just compare diameters

This is the mistake that catches people out. A 9 inch round is only about 12 percent wider than an 8 inch round, so it seems like a tiny step up. But a pan is three dimensional, and by area a 9 inch round actually holds around 27 percent more than an 8 inch round. Pour an 8 inch recipe straight into a 9 inch pan and your cake will be thin, and the reverse risks an overflow.

One handy shortcut falls out of the maths: if both pans are the same height, the height cancels and you are really just comparing their areas. So for two standard pans of the same depth, enter the same height for each and let the tool compare capacity. That is also why an 8 inch square and a 9 inch round come out nearly identical, since both work out to about 64 square inches.

A word on baking time

The factor scales your ingredients, but it does not scale the oven. Baking time does not move in step with the volume, so do not multiply the time by the same number. As a rule, a wider or shallower cake bakes faster, so start checking 10 to 15 minutes early, and some bakers nudge the temperature up by about 25 degrees Fahrenheit. A smaller or deeper cake bakes slower, so it often wants a slightly lower temperature and a longer time. Fill any pan only about halfway to two thirds, and bake any spare batter separately.

One limit to keep in mind: this works for plain round, square, and rectangular pans. Shaped pans like bundt, tube, angel food, and springform are designed around their own forms, so the simple volume sum does not capture them well. Those are best kept in the pan the recipe intended.

Questions people ask

References

1. King Arthur Baking. Why the Size of Your Baking Pan Matters So Much. https://www.kingarthurbaking.com/blog/2025/08/18/baking-pan-size