Macronutrient Ratio Calculator
Calculate how many grams of protein, carbohydrates, and fat you need based on your total daily calorie intake and dietary goal.
Formula
Step 1 — Macronutrient Calories:
Protein kcal = Total Calories × (Protein% ÷ 100)
Carb kcal = Total Calories × (Carb% ÷ 100)
Fat kcal = Total Calories × (Fat% ÷ 100)
Step 2 — Macronutrient Grams (Atwater factors):
Protein grams = Protein kcal ÷ 4 (4 kcal per gram)
Carb grams = Carb kcal ÷ 4 (4 kcal per gram)
Fat grams = Fat kcal ÷ 9 (9 kcal per gram)
Example (2,000 kcal, Balanced 30/40/30):
Protein: 2000 × 0.30 = 600 kcal → 600 ÷ 4 = 150 g
Carbs: 2000 × 0.40 = 800 kcal → 800 ÷ 4 = 200 g
Fat: 2000 × 0.30 = 600 kcal → 600 ÷ 9 = 66.7 g
Assumptions & References
- Uses the Atwater general factors: protein = 4 kcal/g, carbohydrates = 4 kcal/g, fat = 9 kcal/g (Atwater & Bryant, 1900; FDA 21 CFR §101.9).
- Preset ratios are based on common dietary guidelines: Balanced aligns with USDA Dietary Guidelines (2020–2025) AMDR ranges (protein 10–35%, carbs 45–65%, fat 20–35%); Ketogenic follows clinical ketogenic diet protocols (≤10% carbs).
- Alcohol (7 kcal/g) is not included; calories from alcohol will reduce the accuracy of the split.
- These targets are general estimates. Individual needs vary based on age, sex, activity level, health status, and metabolic rate. Consult a registered dietitian for personalised advice.
- Calorie input range: 500–10,000 kcal/day to exclude physiologically implausible values.
- Reference: Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press, 2005.