How this calculator works
This calculator splits a daily calorie target into grams of protein, carbohydrate and fat. Pick a preset split, or choose custom and set your own percentages, as long as they add up to 100%. Each macronutrient has a fixed energy density, so once you know calories and percentages, grams follow directly.
There is no single correct macro split for everyone. Balanced (40/30/30) is a common general-purpose starting point; low-carb and high-protein presets shown here are illustrative examples, not official recommendations, and many other combinations are used for different goals. If you have a specific protein target in grams per kilogram of body weight, use the protein calculator and enter that number as a custom percentage here. These gram targets are estimates, not medical advice — talk to a registered dietitian for a plan tailored to a specific health condition.
The formula
Grams of a macro = (daily calories × percent ÷ 100) ÷ kcal per gramProtein: 4 kcal/g. Carbohydrate: 4 kcal/g. Fat: 9 kcal/g.These are the standard Atwater energy factors used on nutrition labels. Percentages for the three macros must add up to 100%.
Worked example: 2,000 kcal, balanced split (40/30/30)
- Protein calories: 2,000 × 40% = 800 kcal. Grams: 800 ÷ 4 = 200 g.
- Carb calories: 2,000 × 30% = 600 kcal. Grams: 600 ÷ 4 = 150 g.
- Fat calories: 2,000 × 30% = 600 kcal. Grams: 600 ÷ 9 ≈ 66.7 g.
- Check: 200×4 + 150×4 + 66.7×9 = 800 + 600 + 600 = 2,000 kcal.
Frequently asked questions
Why do my custom percentages need to add up to 100%?
The three macros are meant to account for all of your daily calories. If the percentages don't sum to 100%, the resulting grams either leave calories unaccounted for or double-count them, so the calculator asks you to fix the split instead of guessing.
Which split should I use?
Balanced (40/30/30) works as a general-purpose starting point for most goals. Low-carb and high-protein presets suit specific approaches, and if you already know a precise protein target (for example from the protein calculator), custom percentages let you match it exactly.
Why is fat's calorie value 9 instead of 4?
Fat is more energy-dense per gram than protein or carbohydrate — about 9 kcal per gram, compared with 4 kcal per gram for the other two. This is why a fat-heavy split produces fewer grams for the same number of calories.
Does this account for fiber or alcohol calories?
No. This calculator splits calories only across protein, carbohydrate and fat. Fiber is technically a carbohydrate but contributes fewer usable calories in practice, and alcohol (about 7 kcal/g) isn't one of the three macronutrients tracked here.
If I give protein and carbs the same percentage in a custom split, will they come out to the same number of grams?
Yes — protein and carbohydrate both use 4 kcal per gram, so assigning them equal percentages of your daily calories always converts to the same number of grams for each. Fat needs its own separate percentage, since its 9 kcal-per-gram energy density means the same percentage of calories converts to noticeably fewer grams.