Health & Fitness
BMR Calculator
Estimate the calories your body burns at complete rest, and what your daily needs look like at different activity levels.
Updated 3 Sep 2026
Your basal metabolic rate is about 1,649 calories a day — the energy your body uses at complete rest. Daily needs including activity typically fall between 1,979 and 2,844 calories. These are estimates from the Mifflin-St Jeor equation, not personalised medical advice.
Enter your weight, height, age and sex. The calculator estimates your basal metabolic rate using the Mifflin-St Jeor equation, then shows total daily energy needs across five activity levels.
What is the BMR Calculator?
Basal metabolic rate is the energy your body uses simply staying alive — breathing, circulating blood, maintaining temperature and repairing cells — measured at complete rest.
It typically accounts for 60–70% of total daily energy use. Everything you do on top of that adds to it.
How to use the BMR Calculator
- Enter your weight in kilograms and height in centimetres.
- Enter your age in years.
- Select your sex — the equation uses different constants.
The results show BMR plus estimated total daily needs at five activity levels.
Formula
Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161
Total daily energy = BMR × activity factor
Sedentary × 1.200
Lightly active × 1.375
Moderately active × 1.550
Very active × 1.725
Athlete × 1.900
Mifflin-St Jeor has been found more accurate than the older Harris-Benedict equation for most modern populations, which is why it is used here. Both are population averages: individual metabolic rates vary by roughly ±10% around the estimate even among people with identical measurements.
How the calculation works
The equation weights lean body mass indirectly through weight, height and age. Metabolic rate declines with age as muscle mass falls, which is why the age term is subtracted.
Activity factors then scale the resting figure to account for movement, exercise and the energy cost of digesting food.
Worked example
A 30-year-old man, 70 kg and 175 cm:
- 10 × 70 = 700
- 6.25 × 175 = 1,093.75
- 5 × 30 = 150
- BMR = 700 + 1,093.75 − 150 + 5 = 1,648.75 calories
At a moderately active level (× 1.55), estimated daily needs are about 2,556 calories.
Uses and benefits
- Understand roughly where your daily energy needs sit before setting any target.
- See how much difference activity level makes — often 800 calories or more.
- Use it as a starting point to discuss with a dietitian.
Frequently asked questions
BMR is what you burn at complete rest. Total daily energy expenditure adds the energy used by movement, exercise and digestion. TDEE is BMR multiplied by an activity factor, and is the figure relevant to planning intake.
It is the most accurate of the commonly used prediction equations, but it still estimates within roughly ±10% for most people. Body composition, thyroid function, medication and genetics all cause individual variation the equation cannot capture.
Mainly because lean muscle mass declines. Muscle is metabolically more active than fat, so losing it lowers resting energy use. Resistance training slows that decline considerably.
References
Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990. Estimates vary by roughly ±10% between individuals. Anyone with a medical condition, or who is pregnant or breastfeeding, should consult a healthcare professional rather than relying on a calculator.