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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{ 11 comments… read them below or add one }

Victoria (District Chocoholic) January 10, 2011 at 9:20 am

Very useful post – I have to do this all the time because I use several European recipes, which are usually mass-based, and I just recently got a kitchen scale.

Now the next post we all need is a listing of densities of common ingredients (sugar, brown sugar, white flour, butter, powdered sugar, etc.) so that we don’t have to look up densities ourselves. Laziness overwhelms.

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moderndomestic January 11, 2011 at 11:03 am

Actually, whenever I substitute ingredients (like, say, brown sugar for white) I just use the weights – I don’t use the densities.

I also love having everything in ounces because it makes so much easier to tweak everything. Like, instead of having to add another cup or half a cup or whatever, you can just ad an additional ounce of flour, sugar, etc.

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Victoria (District Chocoholic) January 15, 2011 at 7:38 pm

Right, but what if your recipe is in volume instead of weight? Then you need densities. Which you kindly posted for us :).

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moderndomestic January 15, 2011 at 7:42 pm

Can you give me an example? Do you mean with volume measurements, like in cups?

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Victoria (District Chocoholic) January 16, 2011 at 5:44 pm

Yes, volume measurements like cups. So let’s say I want to convert my favorite chocolate chip cookie recipe to mass (grams). It calls for 2.25 cups of flour, so thanks to your handy-dandy chart from the next post, I know that I need about 325 grams of flour. Neat!

Christine January 10, 2011 at 11:08 am

This concept is useful, but both your formula and all of your math is wrong. 2 x 1 = 2, not 14. 2 x 16 = 32, not .125. I understand where you’re trying to go with this, but for people who aren’t great with math, this is more confusing, not less. The formula should be cups of ingredient A x number of ounces per cup of ingredient A. eg., 2 cups x 7 oz = 14 oz.

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Olga @ MangoTomato January 10, 2011 at 4:02 pm

Jenna is actually mutliplying 2 cups by (7 ounces/1cup). so that’s why it’s 14. Cups get canceled out and you are left with 14 ounces.

It’s just hard to figure out because of the format. but the math is right.

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Linda August 4, 2011 at 2:05 am

Thanks so much for the encouragement. I’m about to enter the Baking portion of my Culinary Degree and it petrifies me.

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moderndomestic August 4, 2011 at 10:05 pm

It’s really not too bad! I’m horrible at math but I really like culinary math because it’s very common sense. I’m sure if you pay attention and work hard you’ll do fine!

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eric November 19, 2011 at 3:30 pm

I too use weights when working in the kitchen but don’t like the decimals that come with ounces when telling my wife a recipe… so I just use grams. I only need decimals when using grams when I measure seasonings out. My pizza sauce recipe uses 1.5g oregano and .5g of cayenne for instance… more or less is bad.
Use a spreadsheet and keep a main ingredient as the constant and all other numbers would change in relationship to that constant. If I want to make 5 pounds of pizza dough I use x amount of flour… the next time I make it I may only want to make 3.6 pounds of pizza dough and the recipe changes as well. If I want to make guacamole I don’t know how much my avocado weighs until I cut it open and remove the seed and skin. At that point I can know what my recipe will be but I first have to know how much avocado I’ll be using.
When I make up my recipes I translate from cups to grams using the dept. of agriculture’s website. I then change all weights in T weights instead of many of them x grams per cup, x grams per ounce, x grams per 1/2 teaspoon. I know that 1T of salt is 18.25g, 1T of dry roasted cashews is 8.6g, and 1T of water is 14.8g. If I translate a recipe into grams and it doesn’t come out right… too wet or dry… too salty or sour or whatever; I merely change do whatever it takes to make it right and then my recipe in my spreadsheet will tell me next time what I need to do to make it perfect. I might also add some comments to my recipe to watch for the next time I make it such as time for a dough to proof in what temp kitchen, how long it takes for my oven to preheat to get whatever results that I desire.

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moderndomestic January 16, 2011 at 5:55 pm

Yes, so you can convert the recipe to grams and then just go from there. I actually want to eventually convert all my recipes to grams eventually because it’s a much more precise measurement and I think it yields better results when you scale them up and down.

Also, if you have a recipe in ounces that you want to convert to grams, 1 ounce = 28.35 grams, so you can convert it that way too.

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