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BMR Calculator

Find your Basal Metabolic Rate — the calories your body burns at rest — and estimate your daily energy needs based on your activity level.

Calculate your BMR

Gender

How to use this calculator

  1. Select your gender.
  2. Enter your age, height in cm, and weight in kg.
  3. Choose the activity level that best describes your typical week.
  4. Click Calculate BMR.
  5. The result shows your BMR (calories at rest) and your estimated TDEE (total daily calories).

What is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body needs to maintain basic physiological functions — breathing, circulation, cell production, and temperature regulation — while completely at rest. It represents the minimum energy required to keep you alive over 24 hours.

BMR accounts for roughly 60–75% of total daily energy expenditure for most people. The remaining calories are used during physical activity and digesting food. Knowing your BMR helps estimate how many calories you need each day to maintain, lose, or gain weight.

Mifflin-St Jeor equation

This calculator uses the Mifflin-St Jeor equation, considered the most accurate BMR formula for most adults by major nutrition organisations.

Men

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

Women

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

Example (male, 30 years, 175 cm, 70 kg)

BMR = 10×70 + 6.25×175 − 5×30 + 5 = 700 + 1093.75 − 150 + 5 = 1,649 kcal

Limitations

  • BMR formulas are population averages — individual metabolic rates can vary by ±15% or more.
  • The formula does not account for muscle-to-fat ratio; a muscular person will likely have a higher true BMR than the formula predicts.
  • Activity level multipliers are estimates. Most people overestimate how active they are.
  • Medical conditions, hormonal disorders (e.g. thyroid conditions), and certain medications can significantly alter actual metabolic rate.
  • BMR naturally declines with age; the formula partially accounts for this but not individual variation in the rate of decline.

Frequently asked questions

What is the difference between BMR and TDEE?+

BMR (Basal Metabolic Rate) is the calories your body needs at complete rest — to keep your heart beating, lungs breathing, and cells functioning. TDEE (Total Daily Energy Expenditure) multiplies your BMR by an activity factor to estimate how many calories you actually burn in a day, including physical activity.

Which BMR formula is most accurate?+

The Mifflin-St Jeor equation, used by this calculator, is considered the most accurate for most non-obese adults by the Academy of Nutrition and Dietetics. Older formulas like Harris-Benedict tend to overestimate BMR slightly.

Does BMR change over time?+

Yes. BMR naturally decreases with age, partly because muscle mass tends to decline and muscle is metabolically more active than fat. Hormonal changes, illness, medications, and significant weight changes can also affect BMR.

Can I use BMR to plan a diet?+

BMR is a useful starting reference, but dietary planning should account for your full TDEE plus individual factors. Eating below your BMR for extended periods is generally not recommended without medical supervision, as it can reduce muscle mass and slow metabolism.

Why does gender affect BMR?+

On average, men have more lean muscle mass than women of the same height and weight, which increases metabolic rate. The Mifflin-St Jeor formula adds 5 kcal for men and subtracts 161 kcal for women to account for this average difference.

Is BMR the same as resting metabolic rate (RMR)?+

They are closely related but not identical. BMR is measured under very strict conditions — fasting, complete rest, neutral temperature. RMR is measured at rest but without such strict controls, so RMR is typically 10–20% higher than true BMR. Most online calculators, including this one, estimate RMR but commonly label it as BMR.

References

Health disclaimer

This calculator is for general informational purposes only and does not replace professional medical advice. Always consult a qualified healthcare provider for personal health concerns.