Baking Math: How to Convert Recipes from Cups to Ounces

by moderndomestic on January 10, 2011

A photo from Mango Tomato* from the Bourbon Street Cupcake baking adventure - and a recipe I converted from cups to ounces.

I’ve written before about how wonderful it is to weigh baking ingredients – scaling is faster, cleaner, and more accurate than using volume measurement. These days, I have very little patience for cookbooks that only use cups and don’t include a weighed measurement. But since many of my favorite recipes are in cups, I’ve gotten pretty good at converting recipes from cups to ounces.

I’m about to throw a couple of formulas at you – but don’t fear! All the math is basic fractions, which you learned in elementary school. Unlike, say, calculus (which I never took), culinary math is very common-sense, even for a math-challenged person like myself.

First, you have to find the weights of your ingredients. I use a section in the back of The Cake Bible, which lists out weights per cup of common baking ingredients (since not everyone has a copy of The Cake Bible sitting on their bookshelf, check back tomorrow for my own guide to common baking weights). Once you know the weight of one cup of sugar (7 oz), it’s easy to figure out that the two cups of sugar weighs 14 oz. The basic formula is:

Ounces of ingredient A
Cups of ingredient A   x 1 cup =  Ounces of ingredient A

For example, to convert two cups of sugar to ounces:

7 ounces of sugar
2 cups of sugar   x 1 cup = 14 ounces of sugar

Now, let’s take a more difficult problem. Say that your recipe calls for two tablespoons of sugar – what do you do? It’s not in cups! Well, you have to do a little more math. I know, I know.

There are 16 tablespoons in one cup. If your recipe calls for two tablespoons of sugar, it’s really asking for 2/16 of a cup. Here’s the formula:

1 cup
2 tablespoons of sugar  x 16 tablespoons
= .125 cups of sugar

Now we know that the recipe is really calling for .125 cups of sugar. Then it’s easy to plug it back into the original formula:

7 oz of sugar
.125 cups of sugar x 1 cup = .875 oz sugar

So for this recipe, we need .875 ounces of sugar.

I’m sure your head is spinning right now. I’m sure you’re thinking, “way too much work when I’m just trying to measure some sugar!” But look at the math – this isn’t hard stuff. Can you multiply two by seven? Then you can convert two cups of sugar to ounces. Do you know very basic fractions? Then you can convert two tablespoons of sugar into cups. Yes, you may have to whip out a calculator for a couple of tricky ingredients, but I do many conversions in my head. And believe me, I was a horrible math student. If I can do it, so can you.

And just think of what you gain by converting recipes – speed, precision, and predictability. For a little bit of extra work, you make the first step to becoming a better, more accurate, more consistent baker.

*Thanks to MangoTomato for use of the picture!

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