How to convert a recipe between different baking pan sizes

You’ve found a cake recipe you want to make, but it calls for a tin you don’t own. You may be able to use one from the cupboard. The two things to check are how much mixture it needs and how the change might affect the bake.

Start with the tins you have

Measure inside the base, not across the rim or handles. For a round tin, measure straight across the middle. For a square or rectangular tin, measure the sides. A loaf tin needs both its length and width.

Enter the recipe’s tin and your replacement in the baking pan converter. It works with centimetres and inches, so you don’t need to convert the measurements first. If you pick a size from the list, check it against your actual tin.

A round cake recipe, a square tin at home

Take a recipe for a 20 cm round tin and a 20 cm square tin. They sound similar, but the square has extra room in its corners.

For a cake about the same thickness, make about a quarter more mixture. If the original recipe uses 200 g of flour, that’s about 255 g for the square tin. Change the other ingredients as well, rather than adding extra flour alone.

The calculator gives you 1.27 for this swap. Enter that number under A multiplier in the recipe scaler, paste your ingredient list, and it will work out the amounts. Its displayed figures are more precise than the rounded kitchen example above.

Or keep the recipe as it is. The mixture will spread into a thinner layer in the square tin. That may be perfectly fine for what you’re making, but it can bake sooner. Start checking before the recipe’s usual finishing time.

Leave room for rising

Taller sides don’t mean you need more mixture. If two tins have the same size and shape at the base, the same amount of batter sits at the same height in both. The taller tin just has more space above it.

Going to a smaller tin is different: the mixture sits deeper, and it could overflow as it rises. Don’t squeeze a whole recipe into a smaller tin simply because the uncooked mixture fits. Follow the recipe’s filling instructions, or make less mixture using the calculator’s suggestion.

The optional capacity figures estimate what a tin could hold right up to the rim. They aren’t recommended amounts of cake mixture.

What if the new recipe calls for part of an egg?

If a whole egg is going to be mixed into the batter, beat it first, then weigh out the portion you need. For half an egg, use half the weight of the beaten egg. Don’t assume every egg weighs the same.

Keep yolks and whites separate if the recipe uses them separately. King Arthur Baking explains this method in its guide to reducing a recipe.

Check the bake, not just the clock

Making more mixture doesn’t mean increasing the baking time by the same amount. Thickness, shape and tin material all matter, and the calculator can’t give you a new oven setting or finishing time.

Keep the recipe’s instructions for judging doneness to hand and start checking early after a swap. Switching from metal to glass or silicone is another reason not to rely on the clock alone. The reducing guide above explains why there’s no fixed calculation for the new time.

Some tins need a different approach

Loaf tins often slope inwards, so the result is only a starting point. Measure yours rather than relying on a “2 lb” label. Bundt tins, ring tins and other shaped moulds aren’t covered by this calculator; their outside width doesn’t tell you how much space is available inside.

For more on suitable swaps, see King Arthur Baking’s guide to alternative pan sizes. And if you’re doubling a recipe, consider using two tins of the original size. That can be simpler than finding one much larger tin, though you’ll still need to check each cake as it bakes.

Last reviewed 2 October 2026.