How to Calculate Macros
You can calculate macros on the back of a receipt. Four steps, no app needed — though the macro calculator does it in two seconds.
- Step 1: BMR via Mifflin-St Jeor. Step 2: TDEE = BMR × activity factor. Step 3: Adjust for goal. Step 4: Set protein and fat by bodyweight; carbs fill the rest.
- Protein gets calculated first because it's a per-bodyweight target, not a percentage of calories.
- Recalculate every 4–6 weeks or after a 5% bodyweight change — not weekly.
Step 1 — Basal Metabolic Rate (BMR)
BMR is what you'd burn lying in bed all day. The Mifflin-St Jeor equation is the most accurate of the common formulas:
- Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
- Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Imperial conversion: 1 lb = 0.4536 kg, 1 in = 2.54 cm.
Step 2 — Total Daily Energy Expenditure (TDEE)
Multiply BMR by an activity factor:
| Lifestyle | Multiplier |
|---|---|
| Sedentary (desk, no exercise) | 1.2 |
| Light (1–3 sessions/wk, mostly seated otherwise) | 1.375 |
| Moderate (3–5 sessions/wk, on feet at work) | 1.55 |
| Hard (6+ sessions/wk, physical job) | 1.725 |
| Very hard (twice-daily training, manual labor) | 1.9 |
Be honest. Most people overestimate by one tier. If in doubt, pick the lower one and adjust after two weeks of tracking.
Step 3 — Adjust for goal
- Fat loss: subtract 15–25% from TDEE
- Maintenance: use TDEE as-is
- Muscle gain: add 10–15%
Step 4 — Set the macros
Order matters: protein first, fat second, carbs last.
- Protein — 0.8–1.0 g per lb (1.6–2.2 g/kg) for most adults; 1.0–1.2 g/lb during a cut. Multiply grams by 4 to get calories.
- Fat — 0.3–0.4 g per lb (0.7–0.9 g/kg). Multiply grams by 9 to get calories. Floor: never below 0.25 g/lb sustained.
- Carbs — whatever calories remain, divided by 4.
Worked example
30-year-old man, 180 lb (82 kg), 5'10" (178 cm), trains 4×/week, wants to lose fat.
- BMR = 10×82 + 6.25×178 − 5×30 + 5 = 1,788 kcal
- TDEE = 1,788 × 1.55 = 2,771 kcal
- 20% deficit = 2,771 × 0.80 = 2,217 kcal target
- Protein = 1.0 × 180 = 180 g (720 kcal)
- Fat = 0.35 × 180 = 63 g (567 kcal)
- Carbs = (2,217 − 720 − 567) ÷ 4 = 233 g
Final: 2,200 kcal · 180 g protein · 230 g carbs · 63 g fat.
How accurate is this?
The Mifflin equation is within ±10% for most people, which sounds bad but isn't — your daily intake varies by more than that anyway. The equation gets you in the right zip code; two to four weeks of tracked weight data tells you whether your real maintenance is 100 kcal higher or lower than predicted.
When to recalculate
- Every 5% bodyweight change (lost or gained)
- After any major lifestyle shift (new job, new training program)
- Every 4–6 weeks if you're in an active cut or bulk
- Not every week. Calculator math doesn't update faster than your body changes.
Skip the math?
If you'd rather not multiply, the macro calculator runs the entire sequence and outputs grams. The math is identical to what's above; it just saves you the arithmetic.
Common questions
Should I use lean body mass instead of total bodyweight?
If you're significantly overweight (over ~25% body fat for men, ~32% for women), yes — use lean body mass for the protein calculation. Otherwise total bodyweight is close enough.
Do I add my workout calories?
No. The activity multiplier already includes them. Adding them again double-counts.
What about non-training activity (NEAT)?
NEAT is captured by the activity multiplier. If your daily steps swing wildly, that's a real source of error in the estimate — see the TDEE guide for adjustments.
Quick adjustments by goal
| Goal | Calorie change | Protein g/lb |
|---|---|---|
| Aggressive cut (high BF) | −25% | 1.0 |
| Moderate cut | −15 to −20% | 1.0–1.2 |
| Maintenance | 0% | 0.7–0.9 |
| Lean bulk | +10–15% | 0.8–1.0 |
Sanity-checking your numbers
Before you commit to a target, check these:
- Protein in grams ≥ 0.7× bodyweight in lb (anything lower will cost lean mass)
- Fat in grams ≥ 0.25× bodyweight in lb (anything lower risks hormone issues)
- Total calories not below 1,200 (women) or 1,500 (men) without medical supervision
- Fiber estimable to 25 g+ (women) / 35 g+ (men) within the carb budget
If any of those fail, the inputs are off. Common fixes: revisit activity multiplier (probably too high), shrink the deficit, or accept that meaningful change requires more food, not less.
FAQ
Should I include cardio in my activity multiplier?
Yes — the multiplier is meant to capture everything you do, including cardio. Don't pick "moderate" and then add 400 kcal for an extra spin class. That's double-counting.
What if my weight isn't moving as predicted after 2 weeks?
The math gave you a starting point. Two weeks of accurate tracking gives you the real number. If you're not changing as expected, adjust calories by 100–200 kcal in the right direction and reassess. Don't recompute the entire formula.
Should women use lower numbers?
The Mifflin equation already accounts for sex (the −161 vs +5 constant). The protein and fat ranges are body-weight based, so they automatically scale. No special "women's macros" required.