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Two modes use the same Atwater general factors common on nutrition labels: protein 4 kcal/g, carbohydrate 4 kcal/g, fat 9 kcal/g. Forward: enter grams → total and per-macro kcal. Reverse: enter a calorie budget and (optionally) a P/C/F weighting → approximate grams for each macro. Ratios you type are normalized to sum to 100% if needed.
Alcohol, sugar alcohols, and fiber-specific rules are not included — this is a compact worksheet, not a substitute for a detailed food database or lab-measured energy values.
Atwater factors: protein 4 kcal/g, carbs 4 kcal/g, fat 9 kcal/g.
Total energy
1940 kcal
Protein
150 g
600 kcal
Carbs
200 g
800 kcal
Fat
60 g
540 kcal
Disclaimer: Illustrative energy math from fixed factors only — not medical nutrition therapy or individualized requirements.