How to calculate carbs per weight in a recipe

How do you calculate the carbs per ounce (or any unit of weight) in a recipe?

Don’t you hate it when you cook something from scratch, expect that your dosage will be right on, and find out that you are quite a bit off? We struggled with it a couple of months before realizing that we were missing a fundamental factor.

You cannot add all the weight of components you are putting in a recipe, divide by the number of carbs of the components you put in, and determine what the number of carbs per ounce the recipe has. Most every time you do that, you will underestimate your carb count by 15-25%! The reason is that, in most recipes, a lot of water will go up in vapor, leaving you with concentrated carbs.

So, the way to do it is as follows:

  • weigh every single item you add into the recipe (including water), and count every carb you put in.

  • this gives you the total carbs in the pot

  • when you are fully done cooking, weigh the FULL amount of food you get. That is a PAIN because it’s really hot, and there is a lot of it, and it’s awkward to do it. Also, because it takes a long time to empty the pot of all the food, half the time you lose the tare value on the scale which causes you to have to do it all again. This is how to do it:

a. weigh a bowl that is big enough to take all the food from the pot

b. transfer all the cooked food in the pot. Take the time you need, it’s delicate.

c. weigh the bowl with the food

d. subtract the weight of the bowl from the total weight you just measured. The result is the weight of the food you cooked.

  • divide the number of carbs you calculated by the weight of the food you just got – this tells you how many carbs per unit of weight you have. You will find out that, most of the time, it is a lot higher than if you had used the weight you put into the pot!

In general, we use grams for the amounts we put into a recipe (because it is more precise), but calculate the final weight in ounces because it is more intuitive when you need to know what to serve.


This is great! Thank you!

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Minor point, but if your scale is big enough, you can just tare the scale with the bowl on top. Fill it with the food, then re-weigh. Of course if you do this you need to be quick enough not to have the scale auto shut-off on you.

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For things like soups and stews, you can get a reasonable approximation by using volume instead of weight.

Just figure out the total amount of carbs that went into the pot, the total volume of the finished product, and the volume of the individual serving.

You can get pots with markings inside to make it easy.


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For us we go by serving, not weight of the final cooked product and then go from there! But this is a good tip too. We’ve also memorized for some stuff about how many carbs a cooked portion contains. So, for insatnce, 56 g of our dry penne pasta roughly weighs about 110 g when it’s cooked.


I agree, we do that all the time for small stuff.

But, if you have a big bowl and it takes you too long to transfer, you lose your tare, so you need to do it all over from scratch. This happens to us often enough that I gave the full procedure as the standard :slight_smile:

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Colour me confused (or just lacking sufficient coffee so far). If you know the carb content of the dry pasta, why would you need to know what it weighs after it’s cooked? You weigh your pasta, multiply by 0.7 (if weighing in grams) for the carb, cook the pasta, combine with sauce, portion out and serve. Even if you were making something like a big pasta salad for a crowd, where it is tricky to estimate how much pasta is actually in each portion, you still know the total carb in the bowl.

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Then you might like a scale with a longer shut-off time. Mine stays on for 6 minutes inactive, and on some models you can disable the auto shut-off.

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For simple food items like such as described, this is our approach. I weigh out the dry pasta for two servings and use the carbs as per the side of the box. Cook it. When done, split it into two servings. As @Beacher says, I don’t have to deal with how much the weight has changed.

I can eyeball the split of the cooked pasta into two equal servings pretty good. But often I do use the scale to verify the split into the two servings is equal.

Basically the same @Beacher approach with a more complex food like quiche when it can relatively easily be served into similar sized pieces. Add the carbs of the ingredients and divide by the number of servings. This is where is changes from a “math” problem for me to an “engineering” problem. It just doesn’t matter to me if one slice is 5% different size from another slice. Whether we call it 20 carbs or 21 carbs - it just is not going to make a difference at the end of the day.

We have no gourmet restaurant in my kitchen so our overall approaches are certainly going to be significantly less sophisticated than many others with higher interest and experience as relates to cooking.


I guess when I’m cooking pasta I make enough for the whole family and then we don’t necessarily portion it out evenly (my husband will eat double what the kids eat, for instance). So it’s nice to be able to ladle out one portion for the kids just into their bowls and another for the parents. And I don’t have to do any multiplication, division or subtraction. I don’t have to tare a large bowl, or weigh the whole shebang. I literally have to just weigh one bowl of pasta for Samson and the rest I can eyeball.


I have the same habit. We make pasta for a couple of meals, then we’ll weigh variable portions over several meals. So we need to know the prepared carb content per unit of weight.

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For me, the reason why I weigh the whole recipe after I cook something, is for the times when my son wants a different portion. That way I can just reference my recipe, and ask him how much he wants to eat. I weigh it on the scale while asking him how much he wants. Then he can feel like a normal person and not be limited by the portion on the box.