How much protein do I need per day?

1.6 g per kg of body weight (about 0.73 g per lb) covers the vast majority of people, cutting or bulking — that's where the muscle-retention research plateaus. The old '1 g per lb' rule isn't harmful, just higher than needed; treat it as a ceiling, not a floor. A 180 lb lifter lands around 130 g either way you round.

Do I have to hit my macros exactly?

No. Within ±5–10 g on protein and ±100 kcal on calories, day after day, beats nailing them Monday and abandoning them Thursday. Calories and protein are the two that matter most; carbs and fat can trade places freely at the same calorie total.

When should I recalculate?

Every 10 lb (5 kg) of body-weight change, or whenever your activity level genuinely shifts — a new job on your feet, adding two training days. Also recalculate if 3–4 weeks of honest tracking moves the scale differently than your goal predicts: your real TDEE is whatever the scale says it is.

Why only a 20% deficit for cutting?

Bigger deficits lose more muscle, tank training quality, and rebound harder. At −20% a typical lifter loses roughly 0.5–1% of body weight per week while keeping strength — sustainable for months. If you're impatient, tighten adherence before you tighten calories.

Are carbs at night bad? Should I try keto instead?

Meal timing barely moves the needle next to daily totals — eat your carbs when you like them, including around training and at night. Keto works for some people purely because it controls appetite; it has no fat-loss magic at matched calories and protein, and it makes hard training harder to fuel.

Do these numbers work for women?

Yes — the Mifflin-St Jeor equation has separate male/female constants, and the split logic is identical. Women's absolute numbers come out lower because of body size, not different rules. Very lean athletes of either sex may want protein nearer 2 g/kg while cutting.

How to Calculate Your Macros

Three numbers decide whether your training shows: calories, protein, and consistency. Here's the whole calculation — maintenance, goal, split — with the math shown, a worked example, and a free calculator that does it for you.

8 min read · Updated July 2026

A grid of whole foods — chicken breast, salmon, rice, broccoli, avocado, eggs, oats, and blueberries — photographed on white.

Why macros, not just calories

Calories decide whether your weight goes up or down. Macros decide what the weight is made of. Two people can eat the same 2,200 kcal — one loses fat and keeps muscle, the other loses muscle and keeps soft. The difference is almost always protein.

Only three numbers actually carry the plan:

Calories — the energy budget. Deficit = weight loss, surplus = weight gain, no exceptions that survive four weeks of honest tracking.
Protein — the keep-muscle signal. It also blunts hunger harder than carbs or fat, which is half the battle in a deficit.
Consistency — not a macro, but the multiplier on both. A plan you hit six days out of seven beats a perfect plan you hit twice.

Carbs and fat matter less than the internet suggests: once protein and calories are set, they're mostly a preference slider.

Step 1 — find maintenance (TDEE)

Start with your basal metabolic rate — what your body burns doing absolutely nothing. The Mifflin-St Jeor equation is the standard:

Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161

Then multiply by an activity factor to get your total daily energy expenditure — maintenance calories:

Lifestyle	Multiplier
Sedentary — desk job, little exercise	× 1.2
Light — 1–3 workouts a week	× 1.375
Moderate — 3–5 workouts a week	× 1.55
Very active — 6–7 workouts a week	× 1.725
Athlete — hard daily training	× 1.9

Step 2 — pick the goal adjustment

Maintenance is the reference line. Your goal moves you off it — moderately:

Goal	Adjustment	What to expect
Cut	−20%	≈ 0.5–1% of body weight lost per week, strength mostly held
Lean cut	−10%	Slower loss, easiest to sustain, best for staying strong
Maintain	0%	Recomposition territory for newer lifters — same weight, better shape
Lean bulk	+10%	≈ 1–2 lb gained per month, mostly muscle if training is honest

The percentages are deliberately tame. A crash cut sheds muscle and rebounds; a “dreamer bulk” adds fat you'll spend next year cutting. Boring numbers, compounding results.

Step 3 — split calories into macros

With the calorie target set, the split is three short steps in order:

Protein first: 1.6 g per kg of body weight (≈ 0.73 g/lb). This is where the muscle-retention research plateaus — more won't hurt, but it buys little. Protein is 4 kcal per gram.
Fat second: 25% of calories. Enough for hormones and for meals to feel like meals. Fat is 9 kcal per gram.
Carbs get everything left. Total calories minus protein and fat calories, divided by 4. Carbs fuel training, and training is why the deficit turns into fat loss instead of shrinkage.

A worked example

A 30-year-old man, 5'10" (178 cm), 180 lb (82 kg), training four days a week, cutting:

BMR: 10×82 + 6.25×178 − 5×30 + 5 = 1,788 kcal
TDEE: 1,788 × 1.55 = ≈ 2,770 kcal
Cut −20%: ≈ 2,215 kcal/day
Protein: 1.6 × 82 = 131 g (524 kcal)
Fat: 25% of 2,215 ÷ 9 = 62 g (554 kcal)
Carbs: (2,215 − 524 − 554) ÷ 4 = ≈ 284 g

That's the whole plan: 2,215 kcal · 131 P · 284 C · 62 F. He should lose roughly a pound a week, holding his lifts — and recalculate around 170 lb.

Hitting the numbers day to day

Calculating macros takes two minutes; the results come from landing near them most days. What makes that stick:

Track, at least at first. Two weeks of honest logging recalibrates your portion instincts permanently. Most people discover their “roughly 2,000 kcal” day was 2,700.
Protein at every meal. Hitting 130 g is easy across four meals and nearly impossible in one.
Plan tomorrow, don't autopsy today. Planning meals ahead turns tracking from a confession into a shopping list.
Judge by the trend, not the day. Daily scale weight is noise; the two-week average is signal.

RepDriver's macro counter is built around exactly this loop: set the targets from the calculator, then log or plan each day against a 200-food USDA library — with photos, custom foods, and per-meal running totals. It's free, and it lives next to your training plan.

Common questions

How much protein do I need per day?: 1.6 g per kg of body weight (about 0.73 g per lb) covers the vast majority of people, cutting or bulking — that's where the muscle-retention research plateaus. The old '1 g per lb' rule isn't harmful, just higher than needed; treat it as a ceiling, not a floor. A 180 lb lifter lands around 130 g either way you round.
Do I have to hit my macros exactly?: No. Within ±5–10 g on protein and ±100 kcal on calories, day after day, beats nailing them Monday and abandoning them Thursday. Calories and protein are the two that matter most; carbs and fat can trade places freely at the same calorie total.
When should I recalculate?: Every 10 lb (5 kg) of body-weight change, or whenever your activity level genuinely shifts — a new job on your feet, adding two training days. Also recalculate if 3–4 weeks of honest tracking moves the scale differently than your goal predicts: your real TDEE is whatever the scale says it is.
Why only a 20% deficit for cutting?: Bigger deficits lose more muscle, tank training quality, and rebound harder. At −20% a typical lifter loses roughly 0.5–1% of body weight per week while keeping strength — sustainable for months. If you're impatient, tighten adherence before you tighten calories.
Are carbs at night bad? Should I try keto instead?: Meal timing barely moves the needle next to daily totals — eat your carbs when you like them, including around training and at night. Keto works for some people purely because it controls appetite; it has no fat-loss magic at matched calories and protein, and it makes hard training harder to fuel.
Do these numbers work for women?: Yes — the Mifflin-St Jeor equation has separate male/female constants, and the split logic is identical. Women's absolute numbers come out lower because of body size, not different rules. Very lean athletes of either sex may want protein nearer 2 g/kg while cutting.

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