This is a story all about how I get fed up with having the wrong sized tin for the recipes I find online or in may beloved books. It’s not always easy to figure out the best, most accurate way to convert other people’s recipes to your tin, and it can add an unpleasant margin of error that may spoil the outcome. For starters, most recipes will use imperial measurements for tins (use a 9 inch baking tin, etc) and the ones you buy in a Supermarket or Department Store will be sold in metric measurements. It’s not a lot, but it does bother me. Also, it’s not like you should have to buy a new tin every time you want to try out a new recipe, just because the instructions say so. No, we should be better at dealing with discrepancies like this. Even though it is a pain.
For the sake of convenience, we’re looking at circular tins here. So the subject is cakes and tarts. For a given recipe, you should always be able to work out what quantities are accurately required to fill a tin of any size. The area of the tin is what we care about, as we’re still planning the cake to rise approximately the same amount.
A scaling factor is a multiplication you can apply to all ingredients and it’s derived from the size of the tin you will be using in comparison to the recipe guideline.
Scaling factor based off an 8 inch / 20.32 cm circular tin
- 20cm: x 1.00
- 21cm: x 1.07
- 22cm: x 1.17
- 23cm: x 1.28
- 24cm: x 1.40
- 25cm: x 1.51
- 26cm: x 1.64
- 27cm: x 1.77
- 28cm: x 1.90
- 29cm: x 2.03
- 30cm: x 2.18
But what if your recipe suggests a 23 cm tin and you only have a 20 cm or 8 inch tin? Well I’ve knocked up a handy little calculator below which will tell you the number you should multiple your ingredients by if your pan is different to the original recipe.
Wait, you ask, how do I easily get 1.5 times an egg? Well, yeah consider the scaling factor a guideline. I, and my lazy outlook on baking, recommend you do not measure out 1.765 times an egg in a recipe to meet your tin’s need (unless you’re making macarons), instead consider a slight over-egged mixture, or making too much and making the quantities 1.5 or 2 times the original recipe if your tin is larger than 20 cm. For 1.5 times a large egg, you might simply consider 2 medium eggs. All other measurements can be increased at either 1.5 or 2 times the original, it’s usually just eggs making our lives difficult. Depending on the recipe, with your leftover mixture you can make some mini cakes or tarts with muffin tins.
Baking times aren’t so easy to scale though. It’s best to leave it 5 minutes either way, depending if you’ve scaled up or down and generally keep an eye on it.