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Free Online Tool

BMR Calculator

Calculate how many calories your body burns at rest.
Uses the gold-standard Mifflin-St Jeor equation.

Mifflin-St Jeor Equation

Learn

What Is Basal Metabolic Rate (BMR)?

Understanding BMR is the foundation of any effective nutrition or weight management plan.

The Science of BMR

Your Basal Metabolic Rate is the number of calories your body requires to sustain itself while at complete rest. Even while sleeping, your body is constantly performing vital functions — maintaining heartbeat, breathing, regulating body temperature, producing hormones, repairing cells, and filtering blood through the kidneys.

BMR accounts for roughly 60–75% of total daily calorie expenditure for most people, making it the single largest component of your energy needs. Understanding your BMR helps you set a baseline for any calorie counting, weight loss, or muscle-building plan.

The Mifflin-St Jeor equation used by this calculator is considered the most accurate formula for estimating BMR in non-obese adults. It was developed in 1990 by M.D. Mifflin and S.T. St Jeor and validated across multiple large-scale studies.

Factors That Affect BMR

Body Composition

Muscle burns ~3× more calories at rest than fat tissue. Higher muscle mass = higher BMR.

Age

BMR decreases ~1–2% per decade after 20 due to natural muscle loss (sarcopenia).

Sex

Men typically have higher BMR than women due to greater muscle mass and lower body fat percentage.

Height

Taller individuals generally have higher BMR because they have more body surface area and greater organ mass.

Hormones

Thyroid hormones significantly regulate metabolic rate. Hypothyroidism lowers BMR; hyperthyroidism raises it.

The Math

BMR Formula — Mifflin-St Jeor Equation

For Men

BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5

Example: 30-year-old man, 75 kg, 180 cm
BMR = (750) + (1125) − (150) + 5 = 1,730 kcal/day

For Women

BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161

Example: 30-year-old woman, 60 kg, 165 cm
BMR = (600) + (1031.25) − (150) − 161 = 1,320 kcal/day

Common Questions

BMR Frequently Asked Questions

What is BMR?
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest to maintain vital functions — breathing, circulation, and cell repair. It's the minimum energy required to stay alive.
How is BMR different from TDEE?
BMR is calories burned at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor to account for daily movement. TDEE represents your total daily calorie burn.
Does BMR change with age?
Yes. BMR decreases by about 1–2% per decade after age 20, primarily due to natural muscle loss. Building and maintaining muscle through resistance training is the best way to slow this decline.
How can I increase my BMR?
Build muscle through resistance training. Muscle tissue burns significantly more calories at rest than fat. Adequate protein intake supports muscle retention and has a higher thermic effect than carbs or fats.
Which BMR formula is most accurate?
The Mifflin-St Jeor equation is currently considered the most accurate for non-obese adults. It outperforms the older Harris-Benedict equation in most studies. For obese individuals, the Katch-McArdle formula (which uses lean body mass) may be more accurate.

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