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Rounding & math

Rounding & math insights — evidence-backed explanations of US nutrition labeling, every number traced to 21 CFR.

Do the calories in USDA's branded food data add up?

5,953 branded foods in USDA FoodData Central (release 2026-04-30) state calories that the 4/4/9 rule cannot explain, even after allowing for label rounding, fiber and sugar alcohols. The rule is 4 calories per gram of protein and carbohydrate, 9 per gram of fat. We checked 450,408 foods. 20,463 miss their stated calories by more than 10 calories and more than 20% per 100 g, and about half of those are label rounding. These are USDA's copies of the labels, not the packages themselves, so a gap can also start in USDA's data.