Power Calculators

🔥 BMR Calculator

Calculate your Basal Metabolic Rate from your age, sex, height and weight using the Mifflin-St Jeor equation.

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Enter details

Select male or female for the Mifflin-St Jeor equation.
Enter your age in completed years.
Enter your height in centimetres.
Enter your body weight in kilograms.

Fill in the details and click Calculate to see your results.


Also available in our Android app, with charts and full breakdown tables.

📘 About the BMR Calculator

Basal Metabolic Rate, commonly called BMR, is an estimate of the energy your body needs to support essential functions while at rest.

This calculator uses the Mifflin-St Jeor equation, a widely used predictive equation for estimating resting energy expenditure from sex, age, height and body weight.

The original Mifflin-St Jeor research developed the equation from measurements of resting energy expenditure in 498 healthy adults aged 19 to 78 years.

The result is an estimate rather than a direct measurement. Actual energy expenditure can differ between individuals because metabolism is affected by many biological and environmental factors.

✏️ Worked examples

Example 1 - Male adult

You enter
SexMale
Age30 years
Height175 cm
Weight75 kg
You get
Estimated BMR (kcal/day)1,699
Estimated BMR (kJ/day)7,108

A 30-year-old male who is 175 cm tall and weighs 75 kg has an estimated BMR of about 1,649 kcal per day.

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Example 2 - Female adult

You enter
SexFemale
Age30 years
Height165 cm
Weight60 kg
You get
Estimated BMR (kcal/day)1,320
Estimated BMR (kJ/day)5,524

A 30-year-old female who is 165 cm tall and weighs 60 kg has an estimated BMR of about 1,320 kcal per day.

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Example 3 - Male adult

You enter
SexMale
Age45 years
Height180 cm
Weight90 kg
You get
Estimated BMR (kcal/day)1,805
Estimated BMR (kJ/day)7,552

A 45-year-old male who is 180 cm tall and weighs 90 kg has an estimated BMR of about 1,805 kcal per day.

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Example 4 - Female adult

You enter
SexFemale
Age35 years
Height160 cm
Weight65 kg
You get
Estimated BMR (kcal/day)1,314
Estimated BMR (kJ/day)5,498

A 35-year-old female who is 160 cm tall and weighs 65 kg has an estimated BMR of about 1,314 kcal per day.

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🧭 How to use this calculator

What you enter

  • SexSelect male or female for the Mifflin-St Jeor equation.
  • Age (years)Enter your age in completed years.
  • Height (cm)Enter your height in centimetres.
  • Weight (kg)Enter your body weight in kilograms.

What you get

  • Estimated BMR (kcal/day)
  • Estimated BMR (kJ/day)

💡 Mifflin-St Jeor equation

  • For men: BMR = 10 x weight in kg + 6.25 x height in cm - 5 x age + 5.
  • For women: BMR = 10 x weight in kg + 6.25 x height in cm - 5 x age - 161.
  • The calculator reports the result in kcal per day.
  • The result is also converted to kJ per day using 1 kcal = 4.184 kJ.

💡 What BMR means

  • BMR represents the estimated energy required to support basic physiological functions while at rest.
  • It is not the same as the number of calories you burn during a normal day.
  • Walking, working, exercising, digestion and other activities require additional energy.
  • Your total daily energy expenditure is therefore higher than your BMR for most people.

💡 BMR versus TDEE

  • BMR is the estimated resting energy requirement.
  • TDEE means total daily energy expenditure and includes activity and other components of daily energy use.
  • An activity multiplier is commonly applied to an estimated resting energy expenditure when estimating daily calorie needs.
  • This calculator intentionally calculates BMR only and does not estimate TDEE.

💡 Why BMR changes

  • Body weight affects the calculated result.
  • Height affects the calculated result.
  • Age affects the calculated result.
  • The Mifflin-St Jeor equation uses sex-specific constants.
  • Changes in body composition, health status, hormonal state and other factors can also affect actual energy expenditure.

💡 How to use your BMR result

  • Use BMR as a baseline estimate rather than as a recommended daily calorie intake.
  • For daily calorie planning, BMR needs to be considered together with physical activity and other energy expenditure.
  • For weight management, calorie targets should be based on your overall needs and goals rather than BMR alone.
  • Individual results can differ from a formula estimate, so real-world changes in body weight and professional advice can provide additional context.

💡 Important limitations

  • This calculator estimates resting energy expenditure rather than directly measuring metabolism.
  • The original Mifflin-St Jeor study included healthy adults aged 19 to 78 years.
  • The equation may not be appropriate for every medical or physiological situation.
  • Children and teenagers require age-specific approaches rather than simply applying an adult BMR equation.
  • Pregnancy, lactation, serious illness and other special situations may require individualized energy assessment.
  • A measured resting metabolic rate from indirect calorimetry can differ from a predicted value.

💡 BMR and weight loss

  • BMR should not be treated as a personal minimum calorie prescription.
  • Your calorie requirement for a normal day is generally higher because daily activities require additional energy.
  • A sustainable nutrition plan should consider total energy needs, food quality, activity, body composition and individual circumstances.
  • Very restrictive diets can create nutritional and health concerns and should not be based on a BMR number alone.

❓ Frequently asked questions

What is BMR?

BMR stands for Basal Metabolic Rate. It is an estimate of the energy your body requires at rest to support essential physiological functions.

What formula does this BMR calculator use?

This calculator uses the Mifflin-St Jeor equation. The equation estimates resting energy expenditure from sex, age, height and body weight.

What is the Mifflin-St Jeor equation for men?

For men, the equation is 10 x weight in kg + 6.25 x height in cm - 5 x age + 5.

What is the Mifflin-St Jeor equation for women?

For women, the equation is 10 x weight in kg + 6.25 x height in cm - 5 x age - 161.

Is BMR the same as daily calorie requirement?

No. BMR estimates energy expenditure at rest. A normal daily calorie requirement is higher because it also includes physical activity and other energy expenditure.

Is BMR the same as TDEE?

No. TDEE means total daily energy expenditure and includes energy used for activity and other daily processes. BMR is only the resting component.

How accurate is the Mifflin-St Jeor equation?

It is a predictive equation, so it cannot exactly reproduce an individuals measured energy expenditure. The original study reported a relationship between predicted and measured resting energy expenditure, but individual error remains possible.

Can I use this BMR calculator for children?

This calculator is intended for adults. Children and teenagers have different energy requirements and should be assessed using age-appropriate methods.

Can I use BMR to calculate calories for weight loss?

BMR alone is not a complete calorie target. Daily energy expenditure is higher than BMR because it includes normal activity and other energy costs.

Why is my BMR different from someone with the same weight?

Age, height and sex affect the Mifflin-St Jeor calculation. Actual energy expenditure can also vary because of differences in body composition and other physiological factors.

Why does the calculator show both kcal and kJ?

Kilocalories are commonly used on food labels and nutrition plans, while kilojoules are another standard unit of energy. The calculator provides both for convenience.

Can my actual BMR be different from the calculator result?

Yes. A calculator provides a predicted value. Actual resting energy expenditure can differ between individuals. Indirect calorimetry can be used when a measured value is clinically required.

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