Nutrition Label Calculator

Calories from macronutrients follow fixed conversion factors established by Atwater in the late 1800s and still used today on every nutrition label:

Protein: 4 kcal per gram Carbohydrates: 4 kcal per gram Fat: 9 kcal per gram Alcohol: 7 kcal per gram (not usually labeled)

Total Calories = (Protein x 4) + (Total Carbs x 4) + (Total Fat x 9)

Percent Daily Values (%DV) on US nutrition labels are based on a 2,000 calorie reference diet, updated by the FDA in 2016:

These are reference points, not targets. A 5,000-calorie endurance athlete and a 1,400-calorie office worker have nothing in common here, and the label cannot know which one is reading it.

The rule of thumb printed on every label: 5% or less is a little, 20% or more is a lot. It cuts both ways, working for the things you want to limit (sodium, saturated fat) and the things you want enough of (fiber, protein).

Nested nutrients

Three of the fields on this calculator sit inside another one, exactly as they do on a real label. Saturated fat is part of total fat. Fiber and sugars are part of total carbohydrate. Added sugars are part of total sugars. They are listed separately for information, and they are never added again for calories, which is why the calorie total only uses fat, total carbs and protein. Enter a saturated fat figure larger than total fat and the calculator will tell you, because a real label cannot say that.

Added sugars

The 2016 label update pulled added sugars onto their own line. The reasoning was that the sugar naturally present in fruit and milk arrives with fiber, water and micronutrients, while the sugar stirred into a soda does not, and the older label made the two indistinguishable. The Daily Value is 50 g, which is 10% of a 2,000 calorie diet. A single 12 oz cola is roughly 39 g, so about 78% of the day’s allowance in one can.

Fiber and the calorie count

Fiber is technically worth about 2 kcal per gram rather than 4, since it is only partly fermented in the colon. The FDA permits manufacturers to subtract it, which is where “net carbs” comes from. This calculator uses the straightforward method and leaves fiber in the carbohydrate total, so on a high-fiber food it reads slightly high. It reports the net-carb figure alongside so you can see the difference.

One last thing worth knowing: under FDA rules a label’s calorie count can legally be off by up to 20%, and restaurant nutrition information is generally less accurate than packaged food.