How to Calculate Macronutrient Balance

Splits a daily calorie target between protein, fat and carbohydrate and converts each share into grams. A gram of protein or carbohydrate carries 4 kcal, a gram of fat 9 kcal. Fat packs more than twice as much, so its share in grams comes out smaller still.

This splits a daily calorie target between protein, fat and carbohydrate, and works out how many grams of each that comes to.

\text{grams} = \dfrac{\text{calories} \times \text{share}}{\text{calories per gram}}

A gram of protein or carbohydrate carries 4 kcal, and a gram of fat 9 kcal.

Fat packs more than twice as much

Given the same share of the calories, fat comes out at less than half the grams, because each gram carries 9 kcal. A fat share of 25% sounds generous, but it amounts to only about 55 g a day. A tablespoon of oil is roughly 14 g, so that is four tablespoons.

Example

Splitting 2000 kcal as 20% protein, 25% fat and 55% carbohydrate gives $2000 \times 0.2 \div 4 = 100$ g of protein, $2000 \times 0.25 \div 9 = 55.6$ g of fat and $2000 \times 0.55 \div 4 = 275$ g of carbohydrate.

Notes

Check the total share in the output to see whether it adds to 100%. The calculation runs either way, but anything short or over means the calories do not match the target.

Commonly cited reference ranges are 13 to 20% protein, 20 to 30% fat and 50 to 65% carbohydrate.