BMR: Mifflin Formula, Calculation & How to Raise It

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BMR

M 25y 170cm 65kg

1,593 kcal

M 40y 172cm 75kg

1,630 kcal

F 25y 160cm 52kg

1,234 kcal

F 40y 162cm 60kg

1,252 kcal

Key Takeaways

Mifflin (most accurate): men 10×kg + 6.25×cm − 5×age + 5; women same − 161

Example: 70kg, 175cm, 30yo man → 700 + 1,093.75 − 150 + 5 = 1,649 kcal/day at complete rest

BMR ≠ needs: multiply by activity factor (1.2-1.9) for TDEE — BMR alone is the starvation floor

Raise it: +1kg muscle ≈ +13 kcal/day resting burn — slow but the only durable lever

Core answer: BMR via Mifflin-St Jeor: men = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; women = same but −161. Example: 30-year-old male, 70kg, 175cm: 700 + 1093.75 − 150 + 5 ≈ 1,649 kcal/day.

The Mifflin formula

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

Mifflin-St Jeor is the accepted best general estimate (~±10% error), replacing the older Harris-Benedict equation.

Worked examples

Person	Calculation	BMR
Male, 30, 70kg, 175cm	700 + 1093.75 − 150 + 5	≈ 1,649 kcal
Female, 28, 58kg, 162cm	580 + 1012.5 − 140 − 161	≈ 1,292 kcal
Male, 45, 85kg, 170cm	850 + 1062.5 − 225 + 5	≈ 1,693 kcal

BMR vs TDEE

BMR: calories burned lying still all day (heartbeat, breathing, temperature) — 60-75% of daily burn
TDEE (total daily energy expenditure) = BMR × activity factor (1.2 sedentary → 1.9 athlete)
Fat-loss intake = TDEE − 300~500, and not below BMR long-term

What moves metabolism

Muscle mass: each kg of muscle burns ~13 kcal/day (fat only 4.5)
Age: −2-3% per decade (mostly muscle loss)
Sex: at equal weight, men run 5-10% higher (muscle share)
Thyroid: hyper raises, hypo lowers (medical — see a doctor)
Dieting history: chronic low-calorie intake triggers metabolic adaptation — BMR can drop 15-30%

Ways to raise it

Strength training: +1kg muscle = +13 kcal/day → 4,745 kcal/year ≈ 0.6kg of fat
Adequate protein: protein's thermic effect is 20-30% of its calories (carbs 5-10%)
Regular meals: avoid the energy-saving mode triggered by long fasting stretches
7+ hours of sleep: sleep loss suppresses leptin and raises ghrelin
NEAT (daily movement): standing, walking, chores — up to 300-500 kcal/day difference

Common mistakes

"My metabolism is slow, that is why I can't lose weight": bigger bodies have HIGHER BMR (maintaining more tissue costs more). Most "slow metabolism" is undercounted intake and overestimated activity. True hypothyroidism needs a hospital diagnosis.
"Eating below BMR speeds up loss": chronically below BMR, the body burns muscle and downregulates metabolism — the harder-and-harder spiral. The floor is ≥ BMR or TDEE −500.
"Coffee/chili boosts metabolism long-term": a 3-5% bump that tolerates quickly — not a fat-loss tool.

Frequently Asked Questions

How do I calculate my BMR?

Mifflin-St Jeor (the standard since 1990): men = 10×weight(kg) + 6.25×height(cm) − 5×age + 5; women = same formula − 161. Example: 30-year-old man, 70kg, 175cm: 700 + 1,093.75 − 150 + 5 = 1,649 kcal. This is what you burn in 24h of complete rest — before any movement, work or exercise.

What is the difference between BMR and TDEE?

BMR is the resting floor (breathing, circulation, cell maintenance — 60-75% of total burn). TDEE = BMR × activity factor: sedentary 1.2, light 1.375, moderate 1.55, heavy 1.725, athlete 1.9. The 1,649 kcal BMR above becomes 1,979 sedentary or 2,556 moderately active. Eating below BMR long-term triggers metabolic adaptation — BMR is the red line, TDEE is the working number.

Why does BMR decrease with age?

The formula subtracts 5 kcal per year — about 2-3% per decade, driven mostly by muscle loss (sarcopenia), not an intrinsic slowdown. Research shows BMR per kg of lean mass stays flat from 20 to 60: people who maintain muscle maintain metabolism. The "my metabolism broke at 40" story is usually "I lost 5kg of muscle over 20 years."

How can I raise my BMR?

Muscle is the lever: each kg of muscle burns ~13 kcal/day at rest vs ~4.5 for fat. Adding 5kg muscle ≈ +65 kcal/day — modest but compounds with training calories. What does NOT work: spicy food/cold water/green tea (single-digit kcal), "metabolism-boosting" supplements (nothing legal moves the needle), frequent small meals (TEF depends on total intake, not meal count).

Is it safe to eat at or below my BMR?

Chronically eating below BMR pushes the body into adaptation: thyroid down-regulation, muscle catabolism, NEAT (fidgeting) suppression — the plateau-and-rebound cycle. Sensible floor: eat between BMR and TDEE, deficit 300-500 kcal from TDEE. Aggressive deficits belong in medically supervised settings, not DIY plans.

Which BMR formula should I use?

Mifflin-St Jeor for most people (best validated in modern populations, ±10%). Katch-McArdle if you know your body fat % — it uses lean mass and handles athletic/overweight bodies better: BMR = 370 + 21.6 × lean mass(kg). Harris-Benedict (1919, revised 1984) overestimates ~5%. All formulas are estimates — calibrate against 2-3 weeks of real weight trend.