Basics #15: Scaling Baking Recipes

This Basics post is way long overdue, but it’s an important issue to get on with.


How do you scale baking recipes?

I can only write about scaling round cake recipes because, well, I don’t like making square or sheet cakes. (Dry corners and what not.)

Over the years, I’ve collected round cake tins in a range of sizes. As of now, my smallest tin is 5 inches in diameter, going up to the largest one I own, which is 9-inches diameter.

I started out with 8- and 9-inches because most recipes seem to call for those sizes. But I was finding myself frustrated because cakes just weren’t getting finished. (I have a theory that it’s an Asian politeness thing to avoid taking the last slice, so no one ever does.)

So my solution to prevent leftovers was to make ever smaller and smaller cakes. I eventually stopped at 5 inches because any smaller and you’ll find yourself in cupcake territory.

So what of those 8/9-inch cake recipes? I had to find a way to downsize them for smaller tins. Here’s what I do:

1. My basic formula for scaling round cake recipes

Okay, this is far from being mathematically sound, but it’s worked for me so far.

If you go down an inch, reduce all ingredient quantities by a third or a quarter, i.e., use 75% of the original recipe (See point 2 to decide which amount to reduce.)
If you go down two inches, reduce all ingredient quantities by half, i.e, use 50% of the original recipe.

For example, 9-inch cake recipe may use 200g unsalted butter. For an 8-inch cake, use 150g butter, and 7-inch, 100g, and reduce all other ingredients accordingly as well.

2. Consider eggs

Eggs come in eggs. (Duh.) You’d ideally use large or extra-large eggs for baking, and their contents (yolk and white minus the shell) add up to about 60g to 65g. (Jumbo eggs can go beyond 70g and can mess up your baking.)

When I say consider the eggs in a recipe, I mean try to scale down a recipe while keeping the eggs whole. For example, for a cake recipe that calls for 3 eggs, you should consider down-scaling everything by a third (and use an inch smaller cake tin) so that you still have 2 eggs in your cake.

But what if you can’t? What if you want to halve the original 3-egg recipe? You have two options:

(1) To get your half egg, break open an egg into a bowl on a weighing scale so that you can weigh the egg’s contents. Beat the yolk and white until they’re well combined, and then simply decant half of it into another bowl (for tomorrow’s breakfast?) and use the remaining half in your recipe.

(2) Err on the side of more. So bite the bullet and use 2 eggs instead of 1.5 eggs. This works very well when your eggs are on the smallish side. Also, use your judgement: Add your eggs, well-beaten, bit by bit to your creamed butter and sugar. If the mixture looks like it’s about to curdle and separate, just drop in a tablespoon of the flour from the recipe.

3. Be careful about leavening agents

Baking powder and baking soda make soft, lovely risen cakes, but they can just as easily be your enemy in a scaled recipe. Put too little and your cake structure may be dense and compact. Put too much and your cake will dome in the oven, and then collapse spectacularly on cooling, leaving a nice big dent in the middle.

These leavening agents don’t always obey the laws of maths (at least the maths I’ve laid out above). This is usually the reason why some recipes might have a disclaimer saying that they don’t scale well. But by and large, I’ve had success just using directly the scaling formula in point 1.

The problem normally comes when you want to make a much larger or smaller cake than the original recipe. I’ve made many 5-/6-inch versions of 8-/9-inch cakes. For example, in a 9-inch cake recipe, you might be called to use 3 teaspoons of baking powder. But to make a 5-inch cake, you technically should be using 3/4 tsp baking powder. I would recommend erring on the side of less in this case, and dropping the baking powder to 1/2 tsp, maybe adding a pinch more if it makes you feel more comfortable.

4. Do not overfill your tin

Never put too much batter in your cake tin. I hate layer cake recipes that tell you to dump all the batter in one tin, bake the cake for an enormously long amount of time, then cut out the layers afterwards. Too much work and stress. 

And more often what happens is that the outside of the cake cooks faster than the inside. So when the oven heat finally reaches the middle, the cake domes out on top. I know a cake tin has been overfilled when the only way to have the entire cake cooked is to have the middle bit crack and rise up.

Generally, I find that batters that fill tins up to 1 inch or 1-1/2 inches cook just fine, so don’t be afraid to leave out batter. So, if you’ve scaled down a recipe, but your cake tins seem to be too full, discard some batter or even bake an additional layer. Thinner cakes cook more evenly and come out flatter.

And that’s about it. Scaling recipes puts your in experimental territory, so just have your wits about you when you’re using a scaled recipe for the first time. Some final pieces of advice: Don’t mess with the oven temperature and check on your cakes five minutes before they’re supposed to be done. All the best!

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