Macro Calculator
Free macro calculator that splits daily calories into protein, fat, and carb grams. Supports cut, maintain, bulk, keto, low-carb, and high-protein presets.
A macro calculator splits your daily calorie target into the three macronutrients (protein, fat, and carbohydrate) so you have a concrete number to aim at for each. Without this split, "eat 2,500 calories" is too vague to act on. With it, you know to hit ~165 g protein, 75 g fat, and the rest in carbs.
This tool sets protein first (2.2 g per kg of body weight, capped at the weight a BMI of 25 implies for your height), fat second (75 g by default, capped at 40% of calories and reduced when protein needs the room), and lets carbs fill whatever calories are left. The order isn't arbitrary: protein is the macro doing the most for the muscle you're trying to keep or build, so it gets locked in before anything competes with it. MuscleBuddy uses the same order, then keeps adjusting the numbers against your weigh-in trend.
How this works
The calculator runs in two stages. First it computes your maintenance calories (TDEE) from the Mifflin-St Jeor BMR formula multiplied by an activity factor (or, at 16 and 17, from the NASEM 2023 Estimated Energy Requirement, labelled as such), then it adjusts that baseline by ±500 kcal depending on whether you’re cutting, maintaining, or bulking. That gives you a target calorie level, but calories alone aren’t enough.
Stage two converts the calorie target into macro grams in a fixed order:
- Protein: 2.2 g per kg of body weight (≈1 g per pound), the top of the range the research supports for trained lifters. Above a BMI of 25 the per-kg figure runs off the population it was measured on, so it is applied to the weight a BMI of 25 implies for your height instead.
- Fat: 75 g baseline (covers hormone production for most adults), capped at 40% of calories so a tight target cannot turn a standard split into a zero-carb one. Keto shifts to 70% of calories from fat; low-carb to 40%. Fat is also what yields when protein and fat together would overshoot the calorie target.
- Carbs: fills the remaining calorie balance, typically 200–400 g for most lifters on a standard split.
Why protein stays high on a cut and a bulk alike: in a deficit it protects the lean mass your body would otherwise be willing to burn, and in a surplus it's the raw material for the muscle you're trying to add. Keeping it up costs you nothing you'd miss.
Why fat starts from a gram figure rather than a percentage: your body builds steroid hormones, testosterone and estrogen, from dietary fat, and very low-fat diets are associated with lower hormone output. Research generally puts a sensible floor somewhere around 0.6–1.0 g/kg, and 75 g clears it for most body weights without you having to do the math. It is a starting point, not an untouchable floor: a flat gram figure is a rising share of a falling calorie target, so it is capped at 40% of calories and gives way to protein when the two cannot both fit.
Why carbs flex: they're the macro tied most directly to how your training feels, and the easiest one to move up and down as the day's calorie target changes. Carb cycling, high days on training and low on rest, is that same idea on a schedule.
Frequently asked questions
- How much protein do I need to build muscle?
- Research consistently lands around 1.6–2.2 grams per kilogram of body weight (roughly 0.7–1.0 g per pound). MuscleBuddy uses 2.2 g/kg for trained lifters in any phase, the top of that range, so you are never the reason it fell short. Those figures were measured on people inside the healthy BMI range, so above a BMI of 25 the app applies them to the weight a BMI of 25 implies for your height rather than to your current weight.
- Why does fat start at 75 grams in the standard split?
- Fat supports hormone production, and the commonly cited floor is around 0.6 g per kg of body weight. 75 g clears that for most adults. It is a starting point rather than a fixed number: on a low calorie target it is capped at 40% of calories, and it gives way to protein when the two would overshoot the target together.
- Do I need to track carbs strictly?
- Carbs fill the calorie balance after protein and fat are set. Hitting your calorie and protein targets matters more than precise carb numbers, but consistent carb intake helps training performance and recovery.
- What is a keto macro split?
- Keto runs ~70% of calories from fat, moderate protein, and under 50 g of carbs per day. The calculator includes a keto preset that auto-shifts fat upward and carbs near zero.
- Should I eat the same macros every day?
- Constant macros work well for cuts and bulks where consistency is the priority. For more advanced goals, carb cycling (high/low days) or refeeds can preserve metabolic rate during prolonged dieting.
- How often should I update my macro targets?
- Every 4–6 weeks, or whenever your weigh-in trend stalls or runs off the rails. Macros that worked a month ago drift out of date as body weight changes.
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