How to Calculate Your Macros: BMR, TDEE and Protein Targets

"Macros" sounds like gym jargon, but the math behind it is three formulas stacked in order: how much energy your body burns at rest, how much you burn across a full day, and how to split your target calories into protein, fat, and carbohydrates. Each step builds on the previous one — once you have them, you have a concrete daily target for every macronutrient.

Step 1 — Basal Metabolic Rate (BMR)

Your basal metabolic rate is the number of calories your body needs just to keep the lights on: breathing, circulation, cell repair, temperature regulation — everything that happens while you're lying completely still. It's the floor of your energy budget, not the ceiling.

The most widely validated formula for estimating BMR is the Mifflin-St Jeor equation, published in 1990 and still the standard used in most clinical and research settings. It uses weight in kilograms, height in centimetres, and age in years:

The only difference between the two equations is the constant at the end: +5 for men, −161 for women. This reflects average differences in lean body mass and body composition between sexes. If you prefer to work in pounds and inches: 1 kg = 2.205 lbs, 1 inch = 2.54 cm.

BMR alone tells you very little about how much to eat — almost nobody lies still all day. That's where the next step comes in.

Step 2 — Total Daily Energy Expenditure (TDEE)

Your total daily energy expenditure is BMR scaled up by an activity multiplier that accounts for exercise, movement, and general lifestyle. The standard multipliers are:

Multiply your BMR by the multiplier that best matches your typical week. The result is your TDEE — the number of calories you need to consume each day to maintain your current weight. Eat above it and you gain; eat below it and you lose.

When in doubt, most people underestimate their activity level slightly. The "moderately active" category — exercise three to five days per week — covers the majority of people who go to the gym a few times a week and have a desk job.

Step 3 — Adjusting for your goal

Once you have TDEE, shifting your calorie target is straightforward:

• Fat loss: eat approximately TDEE − 500 calories per day. A daily deficit of 500 calories adds up to roughly 3,500 calories over a week — and since a pound of body fat stores approximately 3,500 calories of energy, this produces a rate of loss of about 1 lb (0.45 kg) per week.
• Muscle gain / lean bulk: eat approximately TDEE + 250 to +500 calories per day. A smaller surplus (250 cal) minimises fat gain; a larger one (500 cal) supports faster muscle growth but adds more fat alongside it.
• Maintenance / body recomposition: eat at TDEE. Progress is slower, but muscle can be built and fat lost simultaneously, especially for beginners or those returning after a break.

Step 4 — Setting your macro targets

With a calorie target in hand, the final step is splitting those calories across the three macronutrients. Each macro carries a fixed calorie density:

• Protein = 4 calories per gram
• Carbohydrates = 4 calories per gram
• Fat = 9 calories per gram

Protein

Protein is the most important macro to anchor first, especially if you're in a deficit. Research consistently supports a target of 1.6–2.2 g of protein per kg of bodyweight per day (roughly 0.7–1.0 g per lb) to preserve or build lean mass. Higher intakes within this range are appropriate during aggressive cuts or when training intensity is high. There's little evidence of benefit above 2.2 g/kg for most people.

Fat

Fat supports hormone production, fat-soluble vitamin absorption, and satiety. A sensible starting range is 20–30% of total daily calories, which at 9 cal/g works out to a meaningful absolute gram target. Avoid going below approximately 0.5 g/kg of bodyweight — very low fat intakes disrupt hormonal function, particularly for women.

Carbohydrates

Carbs fill whatever calories remain after protein and fat are set. They're the body's preferred fuel for high-intensity exercise, so if training performance matters to you, don't cut them to near zero. There's no universal minimum, but most active people feel and perform better with at least 100–150 g/day.

Worked example: fat-loss target for an 80 kg man

Here's the full calculation for a 30-year-old man, 80 kg, 180 cm tall, moderately active (three to five gym sessions per week), with a goal of losing body fat.

BMR

Using the Mifflin-St Jeor men's formula:

TDEE and cutting target

TDEE = 1,780 × 1.55 ≈ 2,759 calories. Cutting target = 2,759 − 500 ≈ 2,260 calories.

Macro split

Final daily targets: approximately 144 g protein / 63 g fat / 280 g carbs, at roughly 2,260 calories. At a consistent daily deficit of 500 calories, this projects to about 1 lb of fat loss per week — a sustainable pace that preserves muscle when protein is adequate.

How to convert units if you work in imperial

The Mifflin-St Jeor equation takes metric inputs. Quick conversions: divide your weight in pounds by 2.205 to get kilograms; multiply your height in inches by 2.54 to get centimetres. A 6'0" (72-inch) person is 182.9 cm; a 180-lb person is 81.6 kg.

Protein targets expressed per pound are simpler to track for many people: 0.7–1.0 g/lb is the same range as 1.6–2.2 g/kg. For the example above, 144 g ÷ 80 kg = 1.8 g/kg = 0.8 g/lb — comfortably within the recommended range.

The most important thing: treat the output as a starting point

Every formula in this guide is an estimate. BMR equations have a margin of error of roughly ±10%, and the activity multipliers are population averages that don't account for individual metabolic variation, non-exercise activity thermogenesis (how much you fidget, walk, stand), or dietary-induced thermogenesis.

The real feedback loop is this: track what you eat for two to three weeks, track your weight daily (and average it to smooth fluctuations), then compare the trend to your expectation. If you're losing faster than 1 lb/week on your cut, add 100–200 calories. If the scale isn't moving, subtract 100–200. The formula gets you close; the mirror and the scale tell you when to adjust.

None of this requires perfect precision. Hitting your protein target consistently matters more than nailing every gram of carbs and fat. Protein drives satiety and muscle retention — the other two macros are secondary dials you can tune later once the habit of tracking is established.

Figro's guides are educational and do not constitute medical or nutrition advice. Individual needs vary — consult a registered dietitian or physician before making significant changes to your diet. Some pages include affiliate links; if you purchase through them we may earn a commission at no extra cost to you.