Choose metric or imperial units and the estimate updates as you type. The calculation happens locally in your browser, with no account or upload. The result is your resting baseline, not your full daily calorie need. Activity, digestion and exercise belong in a separate TDEE calculation.
Private browser utility / Calculators
BMR Calculator
Runs entirely in your browser - no upload, no sign-up.
Your details
Adult estimate using the Mifflin-St Jeor equation
The published equation uses different constants for female and male bodies.
Basal metabolic rate: 1,370 kcal/day
Live estimate
Basal metabolic rate
1,370kcal/day
Average per hour57.1 kcal/hour
Energy in kilojoules5,733 kJ/day
Your formula
10 × 65 + 6.25 × 165 - 5 × 30 - 161This is an adult screening estimate, not a measured metabolic test or a calorie target.
What is a BMR calculator?
A BMR calculator estimates how many calories your body uses each day at rest to support breathing, circulation, temperature control and other basic functions. This calculator applies the Mifflin-St Jeor equation to your age, height, weight and sex, then shows the result in calories and kilojoules per day.
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How to use
- 01Choose your units
Select metric for centimetres and kilograms, or imperial for feet, inches and pounds.
- 02Enter your details
Choose the sex constant used by the equation, then enter your adult age, height and weight.
- 03Read the live estimate
See your BMR in calories per day, calories per hour and kilojoules per day, plus the exact formula working.
- 04Copy the estimate
Copy the result and formula if you want to save or compare it. Treat it as an estimate, not a prescribed intake.
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Who it's for
- People planning meals who want a resting calorie baseline before considering activity.
- Fitness beginners comparing BMR with total daily energy expenditure instead of treating them as the same number.
- Coaches and students checking the Mifflin-St Jeor working with a clear, reproducible formula.
- Metric and US unit users who want the same calculation without converting height and weight first.
FAQ
Is this BMR calculator free and private?
Yes. The calculator is free, needs no account and performs the formula entirely in your browser. Your age, height and weight are not uploaded for the calculation. You can clear the fields at any time and there is no calculation limit.
What is the Mifflin-St Jeor BMR formula?
For males, the equation is 10 times weight in kilograms plus 6.25 times height in centimetres minus 5 times age, plus 5. For females, the final constant is minus 161 instead. The calculator converts imperial measurements to metric before applying the same equation.
How accurate is a BMR calculator?
A BMR formula gives a population-based estimate, not a direct measurement. The Mifflin-St Jeor equation is widely used for adults, but muscle mass, health conditions, medications and individual biology can shift actual resting energy use. Indirect calorimetry in a clinical setting provides a measured value.
Is BMR the same as TDEE?
No. BMR estimates energy used at rest for essential body functions. TDEE estimates your full daily energy expenditure by accounting for activity and other energy use. Your TDEE should normally be higher than your BMR, so do not use the resting number as a maintenance calorie target.
Can I use the BMR calculator to lose weight?
Use BMR as one input, not as a weight-loss target. A practical calorie plan starts with estimated total daily energy expenditure, then considers a moderate deficit and your health needs. A registered dietitian or clinician can help if you have medical conditions or a history of disordered eating.
Can children use the BMR calculator?
This version is intended for adults aged 18 and older. Children and teenagers have changing energy needs and are better assessed with age-specific pediatric methods. Ask a pediatric clinician or dietitian for guidance instead of relying on an adult Mifflin-St Jeor estimate.