Macro calculator
Calories from the Mifflin-St Jeor equation, split into protein, fat and carbohydrate.
- Runs in your browser — nothing you enter is uploaded
- No sign-up, no quotas, free to use as often as you like
How it works
Two steps: estimate how many calories you burn, then divide them between the three macronutrients. Both steps are estimates, and the second is more a matter of preference than most calculators admit.
Where the calories come from
The Mifflin-St Jeor equation estimates your resting metabolic rate, which is then multiplied by an activity factor. It is the equation most dietitians use because it is the most accurate of the simple ones — but it is still a population average, and individuals vary by several hundred calories in either direction.
The activity multiplier is the weak point
Choosing between moderate and hard swings the result by hundreds of calories, and most people overestimate. If the number the calculator gives you is not producing the change you expect after a few weeks, the multiplier is the first thing to adjust.
The split is largely preference
Protein has the strongest evidence behind it — roughly 1.6 to 2.2 grams per kilogram of body weight supports muscle retention, and the protein-per-kilogram figure is shown for that reason. Beyond hitting protein and enough fat for hormone function, how you divide the rest between fat and carbohydrate mostly comes down to what you find satisfying and can stick to.
Not medical advice
This is arithmetic on a published equation. It does not know your health, medication or history, and it is not a substitute for a doctor or a registered dietitian.
Macro calculator — questions
Which equation does it use?
Mifflin-St Jeor, the one most commonly recommended for its accuracy among simple formulas.
How much protein do I need?
Roughly 1.6 to 2.2 grams per kilogram of body weight for most people training regularly. The figure is shown so you can check.
Why is my weight not changing?
Most often the activity multiplier is too high. Drop it a level and reassess after two or three weeks.
Does the split really matter?
Protein does. Beyond protein and adequate fat, the division between fat and carbohydrate is mostly about what you can sustain.
Is this medical advice?
No. It is a calculation from a published formula, not personal dietary advice.