Calculating Carbohydrates
Mary Jean Renstrom
v1.41, 3-25-99

Don't limit yourself to eating foods that come with Nutritional Information labels. Many cookbooks now list nutritional information for recipes; but what about your grandma's potato salad recipe which has been handed down through the generations? With a little bit of knowledge, and a few basic tools, you can figure the carbohydrate content of any food you eat.

1. Essential Tools

Items you will need to calculate the carbohydrate content of any recipe are:* A good book of carbohydrate values. Your book should list the carbohydrate content of several different increments of "raw" ingredients like flour and potatoes. Some books only offer carbohydrate values for "ready-to-eat" foods or for foods found at restaraunts. While these have their place, they are not going to be useful for this purpose. There is a list of good nutritional value books on the Insulin Pumper's website.

  • A kitchen scale. This should be able to weigh several pounds at a time. (For a recipe such as apple pie, you will need to weigh the apples all together.) It need not be a fancy digital scale, however. You can find scales at restaurant supply houses or "cooking" stores.
  • Measuring cups and spoons. Make sure you have a complete set of measuring spoons and both dry and liquid measuring cups.
  • A calculator. You'll also want to have paper and a pencil.

2. The Basic Procedure

Calculating the carbohydrate content of any recipe involves three simple steps.

  • Looking up and calculating the carbohydrate value of each ingredient in the recipe,
  • adding them together,
  • dividing the total number of carbohydrates in the recipe by the number of servings.

The tricky part can come when the amount of an ingredient in your recipe is not expressed in the same units as it is listed in your carbohydrate book. Another "problem area" can be determining the correct serving size.

2.1 Standard equivalents for measuring with the Imperial (English) system
Here is a list of standard equivalents for the units of Imperial measuring. These can also be found in many cookbooks. It is useful to know this information in case the amount of an ingredient required in your recipe is not the amount listed in your carbohydrate book. Of course, if you cook with the Metric system, you will not need to use these:

  • 1 Tablespoon = 3 teaspoons
  • 1/4 cup = 4 Tablespoons
  • 1 pint = 2 cups
  • 1 quart = 2 pints
  • 1 gallon = 4 quarts

2.2 How much is in a serving?

Sometimes it's obvious...
Some recipes have obvious serving sizes. For instance, if you are making chocolate chip cookies, the serving size is one cookie. (No, it is NOT the entire batch of raw cookie dough!!) In this case, you would bake the entire batch of dough, keeping track of how many cookies your kids swipe along the way. Figure the total amount of carbs in the entire recipe and divide this number by the number of cookies you ended up with (including the "swiped" ones!). I'm sure you know by now that you never end up with the same number of cookies that the recipe says you will. Nobody makes cookies that small! The result is the number of carbs in one cookie. Now, if you decide that the serving size is more than one cookie, that's your business and nobody else's. Just multiply by the appropriate number.

Sometimes it's not...
Other recipes are not so clear-cut, like grandma's potato salad. In cases like this, you will need to measure the total volume of the finished recipe and divide it into what seems like a reasonable serving size. This can be a bit messy the first time you make a recipe because you end up scooping it out of one container into another using a measuring cup. Keep track and compute the total volume. Decide what amount is a reasonable serving size and divide this amount by the total volume. The result is the percentage of the total in one serving. Multiply this percentage by the total number of carbs in the recipe to get the number of carbs per serving. Once you have done this, make a note on the recipe so you'll know that the serving size is 1/2 cup (for example) and how many carbs are in each serving. One of my biggest pet peeves is a recipe that says, "Makes six servings" instead of, "Makes six servings, 1/2 cup each". It is a subtle difference but can make life soooo much easier. :-)

With some recipes, it works better to visually divide the food into equal portions and then measure the volume of one portion. A casserole served in a rectangular flat-bottomed dish can be easily divided in half with a spatula and then again into quarters, or sixths, or whatever you like. Once you have divided it, use a measuring cup to determine how much is in one serving and make a note on the recipe.

Another way to determine the number of carbs per serving is to weigh the finished product, before you serve any of it. This works well for recipes that are transferred into a serving bowl and then served "family style". An example would be stir-fried vegetables. You could weigh the entire stir-fry, and then weigh the portion you wish to eat. Divide the weight of your portion by the weight of the entire recipe to get the percentage of the stir-fry that you are eating. Then multiply this percentage by the total number of carbs in the entire recipe to get the number of carbs in your portion. Of course, for this method to work, you need to have a scale which can be "zeroed" with a pan, platter, or serving bowl on it, so you aren't including the weight of the container in your calculations. This is called a "tare" function, look for this when you are shopping for a scale. You would need to transfer the food from its cooking pan to another container for which the scale has been zeroed. Then zero the scale again for your plate or bowl and measure the food into that. Again, make a note on the recipe telling you what the serving size is and how many grams of carbohydrate are in one serving. Then, the next time you make the recipe, you won't have to go through all the weighing procedures again.

2.3 Using Carbohydrate Factors and Weighing Food in Grams
Rather than measuring the volume, some people prefer to weigh food in grams and use "carbohydrate factors" (also known as gram factors) to figure the carbs. Carbohydrate factors give the amount of carbohydrate in one gram of a particular food. There is a list of carbohydrate factors for several foods in the back of the book, "Pumping Insulin", but it doesn't cover grandma's potato salad. It is easy to figure the carbohydrate factor for any food using a scale which is set to read in grams.

Figure the total amount of carbohydrate in the recipe as described previously and weigh the entire salad (or whatever you are making). Divide the number of carbs for the total recipe by the weight in grams to get the amount of carbohydrate in one gram. This is the carbohydrate factor for that food. Then, weigh your individual portion and multiply the weight in grams by the carbohydrate factor. Again, making notes on the recipe will save you the tedium of weighing the entire recipe each time you make it.

2.4 How do I know which ingredients contain carbohydrate?
Any food that originally started out as a plant contains carbohydrate. This includes all fruits and vegetables, as well as grains. Flour is ground grain so it contains carbs. Pasta is processed grain, so it also contains carbs. In addition to this, many dairy products such as milk and yogurt contain carbohydrate. (I suppose you could think of it as the cow or goat processing the plants...) Eggs also contain a small amount of carbohydrate. If you are unsure of which ingredients to include in your carbohydrate total, look it up in your book; if it has no carbohydrates, the book will say so.

3. An example
Here is a recipe that I recently made. It was originally found on the side of a box of "Minute" brand tapioca. No nutrional information was given for the recipe, although the box does list the nutrional value of the tapioca itself. (This is easy to make and delicious, by the way!)

Tapioca Pudding

1/3 cup sugar
3 Tablespoons MINUTE tapioca
2 3/4 cups milk
1 egg, well beaten
1 teaspoon vanilla

Mix sugar, tapioca, milk, and egg in saucepan; let stand 5 minutes. Then, stirring constantly, cook on medium heat until mixture comes to a full boil. (Pudding thickens as it cools.) Remove from heat, stir in vanilla. Cool 20 minutes; stir. Spoon into dishes. Serve warm or chilled. Store leftover pudding in refrigerator. Makes 6 servings.

Here is the ingredient-by-ingredient break-down of how I calculated the carbs for this recipe:

  • Sugar - My book lists granulated white sugar as having 199.8 carbs per cup. I divided this by 3 to get the amount in 1/3 cup. The answer is 66.6 grams. I would normally round this up to 67 grams.
  • Tapioca - The box lists a serving size of tapioca as being 1 1/2 teaspoons and contains 5 grams of carbohydrate for that serving size. I need to know how much is in 3 Tablespoons. There are 3 teaspoons in a Tablespoon (or to put it another way, 1 1/2 teaspoons equals half a Tablespoon) so 1 Tablespoon of tapioca has 10 grams of carbohydrate. Three Tablespoons has 30 grams.
  • Milk -Cow's milk has 12 grams of Carbohydrate per cup. So I multiplied 12 by 2.75 to get the amount in 2 3/4 cups. It is 33 grams.
  • Egg - 1 large chicken egg (raw) has 0.6 grams of carbohydrate.
  • Vanilla - 1 teaspoon has 0.3 grams of carbohydrate.
    To be honest, I consider the carbs in the egg and vanilla to be negligible and didn't figure them in when I did my calculations. You could include them if you wish.

The total number of carbs in the recipe is 67 + 30 + 33 = 130 grams.

I decided to use 1/2 cup as my serving size and dished the pudding out into bowls using a 1/2 cup measure. It made exactly six servings. So I divided 130 by 6 to get 21.67 grams per serving. I rounded up to 22 grams per 1/2 cup serving.

4. A Few Miscellaneous Thoughts on Carb Counting
There are certain foods I almost always weigh or measure and others that I almost never weigh or measure. In general, the higher the carb content of a food, the more important it is to know the exact amount you are eating. For instance, I always measure or weigh the potatoes, rice, or pasta I eat at dinner. I hardly ever measure the green beans. Of course, I don't weigh or measure my meat, unless it has had some carbohydrate "enhancement" such as meatloaf. I weigh baked potatoes after they are baked and figure 6 grams per ounce. I use a general rule that 1/2 cup of cooked potatoes, white rice, or pasta has 20 grams of carbohydrate. I know this is, perhaps, not exactly precise, but it saves my sanity and works out pretty well.

My life became much easier the day I realized that almost all bread has approximately 13 grams of carbohydrate per ounce. You see, my husband is a terrific bread baker and makes a large portion of our daily bread. He does it the old-fashioned way, without a bread machine. We were having a very hard time trying to convert all his recipes to "carbohydrate known". Especially since he often "invents" his own recipes as he goes. It was almost to the point that he was going to give up baking bread and we would be sentenced to eating grocery store bread because it comes with the nutritional information. We finally noticed that the calculations were coming in very close to 13 grams per ounce. At that point, I told him to put away the calculator and get out the yeast. Now I just weigh each slice of bread as I slice it off the loaf and figure the carbs based on the magic number 13. This works for those lovely bagels from the deli too. (My husband doesn't make bagels, he calls them "defective bread". I still love to eat them, though, and ignore his remarks!)

For me, the best part of pumping is carb counting. But without the pump, carb counting wouldn't be very practical for me. I attribute my improved diabetes control to the ability to count carbs and give precisely the amount of insulin I need. I hope that you will find the information in this article useful. As always, good health, and happy eating!

Copyright Notice
Copyright (c) 1998, Insulin Pumpers and Mary Jean Renstrom
Permission to use, copy, distribute this document for any purpose is hereby granted, provided that the author's / editor's name and this notice appear in all copies and/or supporting documents; and that an unmodified version of this document is made freely available. This document is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY, either expressed or implied. While every effort has been taken to ensure the accuracy of the information documented herein, the author / editor / maintainer assumes NO RESPONSIBILITY for any errors, or for any damages, direct or consequential, as a result of the use of the information documented herein.