How this calculation works
Split an energy amount into protein, carbohydrate and fat grams using percentages you choose. Percentages describe shares of calories, not shares of food weight. Because fat has more energy per gram in this general model, the same calorie share produces fewer grams of fat than of protein or carbohydrate.
Worked example
This example uses illustrative inputs. Your current result is shown above.
At 2,000 kcal with 30% protein, 40% carbohydrate and 30% fat: protein = 2,000 × 0.30 ÷ 4 = 150 g; carbohydrate = 2,000 × 0.40 ÷ 4 = 200 g; fat = 2,000 × 0.30 ÷ 9 = 66.666… g, displayed as 66.7 g. The energy shares add to 600 + 800 + 600 = 2,000 kcal.
Assumptions and limits
- General energy factors are 4 kcal/g for protein and carbohydrate and 9 kcal/g for fat. Food-specific factors, fibre and sugar alcohols can differ on real labels.
- The calorie amount and percentage split are your scenario, not a recommendation supplied by this tool. It does not check dietary adequacy, medical needs or food quality.
- Gram results are rounded to one decimal; multiplying the displayed grams back into calories can leave a small rounding difference.
Questions people ask
Why are 30% protein and 30% fat different gram amounts?
Both receive the same calories, but the model divides protein calories by 4 and fat calories by 9. Grams are therefore different even when energy percentages match.
Does the split tell me how many grams of a food to eat?
No. A food contains a mixture of nutrients, water and other material. Use its nutrition information to translate macro grams into portions.
Why must the percentages add to 100?
The tool allocates the entire calorie amount among these three components. Less than 100 leaves energy unassigned; more than 100 assigns the same energy more than once.