BMR calculation: simple method, reliable formulas and concrete examples

BMR calculation : estimate in minutes the calories your body expends at rest (basal metabolism) to better adjust your daily calorie intake.

• Choose the right formula (simple or with added fat)
• Avoid errors in units and interpretation (BMR ≠ daily requirements)
• Convert your BMR into calories per day (TDEE) based on your activity
• Adapt weight loss / maintenance / muscle gain without starving yourself
• Understanding what causes BMR to vary (muscle, age, sleep, stress)

Looking for a clear and immediately usable BMR calculation

1) BMR: what it's for (and what it doesn't say)

BMR (Basal Metabolic Rate) corresponds to the minimum energy expended by your body at rest to function (breathing, temperature, organs).

What this changes : BMR is your theoretical calorie "floor." But your actual daily needs also include walking, exercise, work, and digestion. For this, we use TDEE (Total Daily Energy Expenditure).

Key takeaway : a good BMR calculation is useful if you then know how to convert it into TDEE and use it with a target (deficit/surplus).

2) The most reliable and simple formula: Mifflin-St Jeor

In practice, the most used formula because it is simple and generally accurate in adults is Mifflin-St Jeor.

Formula (weight in kg, height in cm, age in years)

Male : BMR = 10×weight + 6.25×height − 5×age + 5

Female : BMR = 10×weight + 6.25×height − 5×age − 161

BMR calculation subject to error (due to genetics, muscle mass, hormones). Use it as a starting point, then adjust it based on your actual weight/measurements/energy levels.

3) If you know your body fat percentage: Katch-McArdle formula (often more personalized)

If you have a reasonable estimate of your body fat percentage (correct bioelectrical impedance analysis, DEXA, well-done skinfolds), Katch-McArdle can better reflect your metabolism because it starts from lean mass.

Step 1 : Lean mass (LBM) = weight × (1 − %MG)

Step 2 : BMR = 370 + (21.6 × LBM)

In practical terms: if your %MG is very approximate, stick with Mifflin-St Jeor. A "very precise" BMR calculation

4) Table: examples of BMR (Mifflin) + quick conversion to TDEE

To go from BMR to daily requirement (TDEE), we multiply by an activity factor (see next section).

Note : These are estimates. Your true TDEE is verified over 2–3 weeks (changes in weight + waist circumference + energy level).

5) How to convert your BMR into calories per day (TDEE)

TDEE = BMR × activity factor. Choose the factor that best reflects your reality over the week .

• Sedentary (little walking, sedentary work): ×1.2
• Lightly active (7–10k steps, sport 1–3x/week): ×1.375
• Moderately active (sport 3–5x/week): ×1.55
• Very active (intense sport 6–7 times/week): ×1.725
• Extremely active (physical activity + sport): ×1.9

In practice: if you are hesitating between two, take the lower one, then adjust after 14 days.

6) How to use the result according to your objective

Objective: Maintenance

Target calories ≈ TDEE. Adjust by ±100 to 150 kcal according to your progress.

Weight loss goal (sustainable)

Recommended deficit: −10% to −20% of the TDEE.

• If TDEE = 2300 kcal: target 1850–2070 kcal
• If you are very hungry, sleep poorly, or are irritable: reduce the deficit

What this changes : too aggressive a deficit often lowers adherence, spontaneous activity (NEAT) and performance, which slows progress.

Muscle gain objective (cleaner method)

Recommended surplus: +5% to +12% of the TDEE.

• If TDEE = 2600 kcal: target 2730–2910 kcal
• Monitor your weight and measurements (to avoid rapid weight gain)

Macros (simple guidelines)

• Protein: 1.6–2.2 g/kg/day (useful for both weight loss and weight gain)
• Lipids: 0.8–1.0 g/kg/day (hormones, satiety)
• Carbohydrates: the rest (energy, training)

7) Common errors with a BMR calculation (and how to avoid them)

• Don't confuse BMR with daily requirements : BMR does not include your activity. Calculate your TDEE.
• Using the wrong units : height in cm (not m), weight in kg (not lb).
• Underestimating activity : “I train 3x/week” but 3000 steps/day → often rather light/moderate.
• Overestimating calories burned via watches/apps: use them as a trend, not as the truth.
• Changing everything every day : base your decisions on weekly averages.
• Ignoring recovery : sleep and stress alter hunger, food choices, and spontaneous activity.

8) What really influences BMR (and what you can do about it)

Your BMR is mainly linked to: lean mass (muscle/organs), height/weight, age, sex, genetics.

• Muscle mass : more lean mass → higher BMR (moderately, but real). Prioritize strength training + protein.
• Weight loss : BMR decreases when you weigh less (normal). Hence the benefit of a reasonable deficit.
• Sleep : has a strong influence on appetite and metabolic regulation. See our sleep tips .
• Stress : can lead to snacking and reduce spontaneous activity. See stress & anxiety .
• Hormonal health / thyroid : in case of significant fatigue, feeling cold, hair loss, consult a doctor.

9) Supplements and herbs: what is useful (without promising miracles)

A BMR calculation doesn't magically "boost" itself. Supplements can primarily help with: energy, adherence, sleep, appetite management, and digestion.

• Green tea (catechins + caffeine) : may have a slight effect on energy expenditure and fat oxidation in some individuals, especially those with an active lifestyle. Use with caution if you experience anxiety or are sensitive to caffeine.
• Fiber (psyllium, glucomannan) : can help with satiety and regularity. Hydration is essential.
• Magnesium : useful if deficient/symptoms (cramps, stress, sleep). Can improve comfort, does not "burn calories".
• Adaptogenic plants (e.g., ashwagandha) : of particular interest for stress/sleep in some people; to be discussed according to context and contraindications.

In practical terms: prioritize protein, steps, strength training, and sleep first. Only then should you consider supplements for support. For overall guidance, see well-being and digestion .

10) Validation method: make your BMR calculation “true” within 14 days

The formulas provide an estimate. The best accuracy comes from your monitoring.

• Choose a calorie target based on TDEE.
• Weigh yourself 3–7 times/week upon waking, then calculate an average.
• Monitor waist circumference once a week.
• Keep your steps fairly steady.

Interpretation :

• Stable weight (±0.2%/week): target close to your maintenance.
• Weight is falling too quickly (>0.8%/week): increase by 100–200 kcal.
• Weight does not change in theoretical deficit: decrease by 100–150 kcal or increase steps.

BMR calculation FAQ

Are BMR and RMR the same thing?

Very similar. BMR is measured under very strict conditions, while RMR is a bit more "realistic". In practice, calculators often use the term BMR for an RMR-type estimate.

What is the best BMR calculation?

Mifflin-St Jeor for the majority. Katch-McArdle if you have a good estimate of body fat.

Why does my calculated BMR seem “too low”?

Often because you confuse BMR and TDEE. Multiply by the activity factor to get your maintenance calories.

Does age significantly lower BMR?

It decreases with age, especially if muscle mass declines. Strength training and protein intake limit this decline.

Can you go below your BMR to lose weight faster?

Occasionally possible, but often counterproductive (hunger, fatigue, decreased spontaneous activity). Aim for a moderate and sustained deficit.

My work is irregular: how do I choose the delivery person?

Take the average over 2 weeks (not + workouts). Otherwise, choose the lowest factor and adjust based on the tracking.

Do smartwatches provide a good TDEE?

They are useful for tracking trends, but the error can be significant. Always verify with changes in weight/measurements.

Does a “slow metabolism” exist?

There are individual variations, but most of the time the difference comes from lean mass, total activity (NEAT) and estimated intake.

References

To learn more, here are some reliable sources on energy, metabolism, and weight management:

• PubMed (Mifflin-St Jeor: resting energy expenditure equations)
• PubMed (comparisons of energy expenditure equations)
• WHO (diet/activity and weight management recommendations)
• Harvard Health (Metabolism: Factors and Misconceptions)

If you want to link your calorie goal to a more holistic approach (stress, sleep, digestion), you can also consult our weight loss page .