This macro calculator turns your body stats and goal into daily gram targets for protein, carbohydrates, and fat — the three macronutrients that make up every calorie you eat. It is the same approach used in IIFYM ("if it fits your macros") and flexible dieting: hit your macro numbers each day and total calories take care of themselves.
The calculator first estimates your total daily energy expenditure (TDEE) with the Mifflin-St Jeor equation and your activity level, then adjusts calories for your goal — a 500-calorie deficit to lose weight, maintenance to hold steady, or a 300-calorie surplus to build muscle — before splitting them into macros.
How the Macro Split Is Calculated
Each macronutrient supplies a fixed number of calories per gram: protein and carbohydrates provide 4 calories per gram, while fat provides 9. The calculator allocates your daily calories in three steps:
- Protein first: 0.9 g per pound of body weight (about 2 g per kg) — enough to preserve or build muscle in a deficit or surplus, per sports nutrition research recommending 0.7–1 g/lb
- Fat next: 25% of total calories, which supports hormone production and vitamin absorption (most guidelines recommend 20–35%)
- Carbohydrates last: whatever calories remain, divided by 4
Example allocation at 2,000 calories for a 165-lb person: 149 g protein (594 cal), 56 g fat (500 cal), and the remaining 906 calories as 226 g of carbs. Carbs get the leftover share because they are the most flexible macro — fuel for training rather than a structural requirement.
Macro Targets by Goal
The right macro emphasis shifts with your goal:
- Cutting (lose): calories at TDEE − 500 (≈1 lb/week loss). Protein at the high end — 0.8–1 g/lb — because a deficit increases muscle-loss risk. Keep fat at 20–25% and let carbs absorb the reduction.
- Maintenance: calories at TDEE. Protein of 0.7–0.9 g/lb is plenty; distribute the rest to match preference and training volume.
- Lean bulking (gain): calories at TDEE + 250–300 (≈0.5 lb/week gain). Protein of 0.8–0.9 g/lb; push extra calories mostly into carbs to fuel harder training sessions.
Whatever the goal, spread protein across 3–5 meals of 25–40 g each for the best muscle-protein-synthesis response, and weigh yourself weekly — if two to three weeks pass without expected progress, adjust calories by 100–200 and keep protein fixed.
Example: 165-lb Male Cutting on a Moderate Activity Level
A 30-year-old male, 5'10" and 165 lbs, exercising 4–5 times per week: his BMR by Mifflin-St Jeor is 1,715 calories and his TDEE is 1,715 × 1.465 ≈ 2,512 calories/day.
Choosing the "lose weight" goal subtracts 500 calories: 2,012 calories/day.
- Protein: 0.9 × 165 = 149 g → 149 × 4 = 594 calories
- Fat: 25% × 2,012 = 503 calories → 503 ÷ 9 = 56 g
- Carbs: 2,012 − 594 − 503 = 915 calories → 915 ÷ 4 = 229 g
His daily targets: 149 g protein, 56 g fat, 229 g carbs. At roughly 30% protein, 25% fat, and 45% carbs, this split protects muscle while leaving enough carbohydrate to train hard through the deficit.
Frequently Asked Questions
What are macros?
Macros (macronutrients) are the three nutrients that supply calories: protein and carbohydrates at 4 calories per gram, and fat at 9 calories per gram. Alcohol is a fourth calorie source at 7 per gram but is not a nutrient. "Counting macros" means hitting daily gram targets for each instead of only counting total calories.
How much protein do I need to build muscle?
Research supports 0.7–1 g of protein per pound of body weight per day (1.6–2.2 g/kg) for building or preserving muscle — this calculator uses 0.9 g/lb. For a 165-lb person that is about 149 g daily. Intakes above 1 g/lb show little added benefit for most people.
What is IIFYM?
IIFYM stands for "if it fits your macros," a flexible dieting approach where no food is off-limits as long as your daily protein, carb, and fat targets are met. It works because body composition responds primarily to total calories and macro balance — though food quality still matters for health, fiber, and satiety.
What macro ratio is best for weight loss?
There is no single magic ratio — a calorie deficit drives fat loss, and higher protein (25–35% of calories) protects muscle and controls hunger. This calculator produces roughly 30% protein, 25% fat, and 45% carbs on a cut. Low-carb and low-fat diets show similar results when calories and protein are matched.
Should I count net carbs or total carbs?
This calculator gives total carbohydrates. Net carbs subtract fiber (and some sugar alcohols) since fiber contributes few usable calories. For fat-loss math the difference is minor — aim for 25–38 g of fiber daily within your carb budget. Keto dieters usually track net carbs; everyone else can simply track total.