Cake Pan Conversion Calculator

So you want to bake a cake but the recipe calls for a 20cm round tin and you only have a square one sitting in the cupboard? Don't panic. This little cake pan conversion calculator will tell you exactly what number to multiply your ingredients by so your bake turns out just right - no matter what shape or size pan you're working with.

Why pan size matters more than you think

Baking is not like cooking. You can't just eyeball it. If you pour a recipe meant for a 20cm round tin into a 26cm tin, you'll end up with a flat, dry, overcooked disappointment. Go the other way and use a smaller pan, and your batter will overflow or stay raw in the middle. The size and shape of your pan directly affects how your bake rises, how long it needs in the oven, and how it looks when it comes out.

Round vs square pan. Are they really that different?

Yes, actually. A lot of people assume a 20cm round tin and a 20cm square tin are roughly the same - but they're not. A square pan holds about 25% more batter than a round pan of the same diameter. That's enough of a difference to seriously affect your recipe. This is exactly the kind of thing this calculator handles for you automatically.

How to use cake pan conversion calculator

For example, if you get a result of 1.3, that means you need 1.3x everything. So 200g of flour becomes 260g, 100g of butter becomes 130g - straightforward. But what about eggs? If the recipe calls for 3 eggs, 3 × 1.3 = 3.9 eggs. Crack the extra egg into a small bowl, beat it lightly with a fork, and just use most of it. It doesn't need to be exact - a little more or less egg won't ruin your bake.

If your recipe lists eggs in grams rather than by number, it's actually much easier - just multiply the gram amount like any other ingredient and weigh it out. A medium egg is roughly 50g without the shell, so you can eggs into a bowl, beat them together, and weigh out exactly what you need using a kitchen scale.

What if my pans are different depths?

This calculator is designed for changing the diameter of your pan, not the depth. So if a recipe bakes each layer separately (which is the case for most layer cakes), you can use whatever pan you have and the calculator will do the job perfectly. However, if the recipe specifically calls for a tall pan (4 inches or 10cm deep), like in a Chiffon cake or Genoise, you do need a pan with the same depth. Those recipes rely on the height of the pan to rise and set properly, so swapping to a shallower tin won't work - even if the diameter is right.

What about recipes in cups?

The calculator works with any unit of measurement - grams, ounces, cups, tablespoons, whatever your recipe uses. You're not converting units, you're just multiplying amounts. So if a recipe calls for 2 cups of flour and your multiplier is 1.5, you need 3 cups. Simple as that. However, if you really want consistent results, I'd always recommend baking by weight in grams rather than cups. Cups can vary depending on how loosely or tightly you pack them, and in baking that small difference can actually matter.