Explanation
Macronutrient energy allocation
This calculator converts an energy split that you choose into grams. It does not choose a diet, a calorie target or a recommended macronutrient ratio.
Choose the question and enter values
Enter the energy scenario and three calorie percentages that add to exactly one hundred. Choose which macronutrient’s gram amount to display; the same inputs can be used for all three.
Protein g = E × p ÷ 100 ÷ 4; carbohydrate g = E × c ÷ 100 ÷ 4; fat g = E × f ÷ 100 ÷ 9. E is daily kcal; p, c and f are calorie shares in percent that add up to 100.
| E | Daily energy |
|---|---|
| p | Protein share |
| c | Carbohydrate share |
| f | Fat share |
| A | Age |
Protein at 1,800 kcal a day
| Daily energy | 1,800 |
|---|---|
| Protein share | 20 |
| Carbohydrate share | 50 |
| Fat share | 30 |
| Age | 30 |
| Result | 90 g/day |
Protein grams: 1,800 kcal/day split protein 20%, carbohydrate 50%, fat 30%. The selected share’s calories ÷ 4 kcal/g (protein, carbohydrate) or 9 kcal/g (fat) = 90 g/day. Adult age context: 30.
Carbohydrate in the same scenario
| Daily energy | 1,800 |
|---|---|
| Protein share | 20 |
| Carbohydrate share | 50 |
| Fat share | 30 |
| Age | 30 |
| Result | 225 g/day |
Carbohydrate grams: 1,800 kcal/day split protein 20%, carbohydrate 50%, fat 30%. The selected share’s calories ÷ 4 kcal/g (protein, carbohydrate) or 9 kcal/g (fat) = 225 g/day. Adult age context: 30.
Fat in the same scenario
| Daily energy | 1,800 |
|---|---|
| Protein share | 20 |
| Carbohydrate share | 50 |
| Fat share | 30 |
| Age | 30 |
| Result | 60 g/day |
Fat grams: 1,800 kcal/day split protein 20%, carbohydrate 50%, fat 30%. The selected share’s calories ÷ 4 kcal/g (protein, carbohydrate) or 9 kcal/g (fat) = 60 g/day. Adult age context: 30.
Diagram of this result
The bar splits the daily energy by calorie share. Each part lists its grams: calories ÷ 4 for protein and carbohydrate, ÷ 9 for fat. The split is your scenario, not a recommendation.
The exact numbers and their units are stated in the visible text. Predictions and scenario inputs are not medical measurements or prescriptions.
Common mistakes
A percentage of calories is not a percentage of grams. Fat contributes more energy per gram, so a thirty-percent fat calorie share does not mean thirty percent of the total gram weight.
Assumptions and limits
Adult context 20–120; energy 100–10000kcal/day; each share 0–100% and exact total 100%. General 4/4/9 factors; specific foods, fibre, alcohol and sugar alcohols can differ. No diet prescription, allergies or clinical nutrition assessment. Educational information only, not medical advice, diagnosis or an individualized nutrition plan.
Are the default percentages recommended?
No. They demonstrate the arithmetic only. Appropriate intake depends on individual circumstances and should not be inferred from these defaults.
Method and references
USDA National Agricultural Library describes general energy factors of 4kcal/g for protein and carbohydrate and 9kcal/g for fat: https://www.nal.usda.gov/programs/fnic . These are arithmetic factors rather than an endorsement of a calorie level or distribution.