BMR Calculator
Calculate Basal Metabolic Rate using Mifflin-St Jeor and Harris-Benedict equations.
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Quick Tip
Enter age, sex, weight and height.
About This Tool
Why use BMR Calculator?
Basal metabolic rate is the energy your body uses at complete rest to keep breathing, circulating blood and maintaining temperature. This calculator shows BMR from two published equations — Mifflin-St Jeor and Harris-Benedict — plus your total daily energy expenditure at five activity levels.
Mifflin-St Jeor is the one most dietitians use today: for men, 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women the last term is −161. A 30-year-old woman of 65 kg and 165 cm has a BMR of about 1,375 kcal. Multiplying by an activity factor (1.2 sedentary up to 1.9 for very heavy training) gives the calories she actually burns in a day.
Key Benefits
Two established equations
Mifflin-St Jeor and Harris-Benedict side by side, so you can see the spread rather than trust one figure.
TDEE at every activity level
The whole ladder from sedentary to very active is shown, which makes it easy to see what a change in training would cost.
Honest about precision
These are population averages; individual metabolism varies by roughly ±10%, so treat the number as a starting point.
How to use BMR Calculator
- 1
Enter age, sex, weight and height.
- 2
Read the BMR from both equations; they normally differ by a few percent.
- 3
Pick the activity level that matches a typical week, not your best week.
- 4
Use the resulting TDEE as the starting point for a maintenance, deficit or surplus target.
Best use cases
Find a maintenance calorie target before planning a diet.
See how much more you need to eat when training load rises.
Compare two equations before setting a nutrition plan.
Understand why calorie needs fall with age and with weight loss.
BMR Calculator FAQs
What is the difference between BMR and TDEE?
BMR is what you burn completely at rest. TDEE is BMR multiplied by an activity factor and includes movement, exercise and digestion, so it is the number that matters for eating targets.
Which equation is more accurate?
Mifflin-St Jeor is generally preferred for healthy adults and is the one most guidelines recommend. Harris-Benedict, revised in 1984, tends to read slightly higher.
Why does my BMR fall when I lose weight?
A smaller body needs less energy to maintain. That is why a calorie target set at the start of a diet stops working after a few months and needs recalculating.
How many calories should I eat to lose weight?
A deficit of about 500 kcal a day below TDEE is a common target for losing roughly half a kilo a week. Very low intakes are hard to sustain and should be discussed with a clinician.
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