Recipe Carb Counter

How the calculator works

Each line of your recipe is matched to a food in USDA FoodData Central and converted to grams. The calculator then applies the USDA carbohydrate figure:

carbohydrate in a line = grams / 100 x carbohydrate per 100 g

carbohydrate per serving = total / servings

It does the same for fiber and for total sugars, and shows them under the main result. Open “Show the math” to see the grams of carbohydrate from each ingredient.

Volumes are converted with the USDA weight of a cup of that food. That matters here more than for most nutrients, because the starchy ingredients are the ones people measure by the cup, and a cup of flour (125 g) is nothing like a cup of rice (185 g) or a cup of sugar (200 g).

Worked example

A butter cake: 2 cups flour, 1/2 cup butter, 3/4 cup sugar, 2 eggs, 1 teaspoon baking powder, 1/2 cup milk and 1/4 teaspoon salt. Twelve pieces.

1. All-purpose flour, 250 g: 190.8 g of carbohydrate
2. Granulated sugar, 150 g: 150 g
3. Whole milk, 122 g: 5.9 g
4. Baking powder, 4.6 g: 1.3 g
5. Eggs, 100 g: 0.7 g
6. Butter, 113.5 g: 0.1 g

Total: 348.7 g. Per piece: 348.7 / 12 = 29.1 g, of which 13.1 g is sugars and 0.6 g is fiber.

Flour and sugar are 98 percent of the carbohydrate. Butter and eggs, which carry most of the fat, add almost none. In most baking, counting carbs comes down to counting two ingredients carefully.

What the total is made of

Total carbohydrate is three things added together: starch, sugars and fiber. USDA reports the total, and separately reports sugars and fiber. Whatever is left is mostly starch.

For the cake: 348.7 g total, minus 157 g of sugars, minus 6.8 g of fiber, leaves about 185 g of starch, nearly all of it from the flour.

Some people subtract fiber from the total and call the result net carbs:

net carbs = total carbohydrate - fiber

For a piece of the cake that is 29.1 - 0.6 = 28.5 g. “Net carbs” is not a figure that appears on the FDA’s Nutrition Facts label, which lists total carbohydrate with fiber and sugars beneath it. The calculator gives you total and fiber and leaves the subtraction to you.

Carbohydrate in the staples

Per cup, from the USDA records the calculator uses:

Ingredient	Weight of 1 cup	Carbohydrate	Fiber
Granulated sugar	200 g	200 g	0 g
White rice, uncooked	185 g	148 g	2.4 g
Lentils, dry	192 g	122 g	20.5 g
All-purpose flour	125 g	95 g	3.4 g
Whole wheat flour	120 g	86 g	12.8 g
Rolled oats	81 g	55 g	8.2 g
Potato, diced	150 g	26 g	3.1 g
Whole milk	244 g	12 g	0 g

Two comparisons are worth a second look.

Whole wheat flour has a little less carbohydrate per cup than white flour, 86 g against 95 g, but nearly four times the fiber: 12.8 g against 3.4 g. Swapping one for the other barely moves the total and changes what it is made of.

Lentils and rice are close in total, and far apart in fiber. A cup of dry lentils has 20.5 g of fiber, most of the FDA’s 28 g Daily Value in one ingredient.

Uncooked and cooked

The grain figures are for uncooked food, because that is how recipes list it. Rice and pasta take in water as they cook, so the same carbohydrate ends up spread through a larger volume. A cup of uncooked white rice, at 148 g of carbohydrate, makes about three cups cooked.

So if a recipe says “3 cups cooked rice”, enter “1 cup rice”. If you enter 3 cups, the calculator will take it as uncooked and the result will be three times too high.

Dry pasta has the same trap. Enter the dry weight from the packet.

Reading the result

The FDA’s Daily Values are 275 g for total carbohydrate and 28 g for dietary fiber. Its general guide is that 5 percent of a Daily Value or less per serving is low and 20 percent or more is high.

For the cake: 29.1 g of carbohydrate is 11 percent of 275 g. Its 0.6 g of fiber is 2 percent of 28 g, which is low.

Why your number may differ

How you fill the cup. The USDA cup of flour is 125 g. A cup scooped straight from the bag can weigh more, and every extra 10 g of flour is 7.6 g of carbohydrate.

Counted vegetables. One potato is taken as 213 g, the USDA medium size, with 37 g of carbohydrate. USDA puts a large potato at 369 g.

Thickeners. A tablespoon of cornstarch is 8 g and almost pure carbohydrate, at 91 g per 100 g.

Coatings. Flour or breadcrumbs used for dredging are only partly eaten. The calculator counts the whole amount you list.

Lines not counted. Anything the calculator could not match adds nothing. Read the “Not counted” list.

Tips and common mistakes

Weigh flour, rice and sugar if you can. They are most of the total.

Enter grains and pasta uncooked.

Count the sauces. Ketchup is 27 g of carbohydrate per 100 g and honey 82 g.

Do not forget the milk in baking and in sauces.

Check the servings. Carbs per serving is the total divided by a number you chose.