How the macro calculator works
The calculator runs in three steps. First it estimates the calories your body burns at rest using the Mifflin-St Jeor equation, which uses your sex, age, height and weight. Then it multiplies that by an activity factor to get your maintenance calories, the amount that keeps your weight steady. Last, it adjusts for your goal and divides the result into protein, carbs and fat.
Protein and carbs each have 4 calories per gram and fat has 9. A 2,400 calorie day on the balanced split is 30% protein, 40% carbs and 30% fat, which comes to 180 g protein, 240 g carbs and 80 g fat.
Which macro split to pick
Balanced suits most people and is the easiest to stick to. Higher protein helps you keep muscle while losing fat and keeps you fuller. Lower carb trades carbs for fat, which some people find easier for appetite. Higher carb suits endurance training and long sessions.
Total calories decide whether you gain or lose weight. The split changes how you feel, perform and recover, so pick the one you can follow for months.
How to use your numbers
Treat the result as a first estimate. Eat to it for two to three weeks, weigh yourself a few mornings a week and look at the trend. If your weight is not moving the way you want, change your calories by about 100 to 200 a day and check again.
Common questions
How accurate is a macro calculator?
It is an estimate. Equations like Mifflin-St Jeor are usually within about 10% for most adults, but activity level is a guess. Use the result as a starting point and adjust after two to three weeks based on how your weight changes.
How much protein do I need?
A common target for people who lift is roughly 0.7 to 1 gram per pound of body weight a day (1.6 to 2.2 g per kg). The higher protein split usually lands in that range.
Should I eat the same macros on rest days?
You can. Keeping the same numbers every day is simpler and works well for most people. Weekly totals matter more than any single day.
Do I need to hit my macros exactly?
No. Getting within about 5 to 10 grams of each target, and close on total calories, is accurate enough.