BMR Calculator
Estimate basal metabolic rate with the Mifflin-St Jeor equation.
Basal Metabolic Rate (BMR) is the number of calories your body burns in 24 hours while at complete rest, powering essential functions like breathing, circulation, and cell repair. This basal metabolic rate calculator uses the Mifflin-St Jeor equation, developed in 1990 and widely regarded as more accurate for most people than the older Harris-Benedict equation, and works as a general metabolic rate calculator for anyone who wants a quick bmr online check.
Enter your age, sex, height, and weight to calculate your BMR - the foundation figure used to estimate your total daily calorie needs (TDEE) once activity level is factored in.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Male, 80 kg, 180 cm, 35 years old | BMR ≈ 1,755 kcal/day | BMR = 10(80) + 6.25(180) − 5(35) + 5 = 800 + 1,125 − 175 + 5 = 1,755. |
| Female, 65 kg, 165 cm, 28 years old | BMR ≈ 1,380 kcal/day | BMR = 10(65) + 6.25(165) − 5(28) − 161 = 650 + 1,031.25 − 140 − 161 = 1,380.25. |
Mifflin-St Jeor vs. Harris-Benedict
The Harris-Benedict equation, developed in 1919 and revised in 1984, was the standard BMR formula for decades. The Mifflin-St Jeor equation, published in 1990, was developed using more modern body composition measurement techniques and has been shown in multiple validation studies to more accurately predict resting metabolic rate for most adults, which is why it's now the more commonly recommended formula in clinical and nutrition settings.
What BMR Does and Does Not Tell You
BMR alone is not your total calorie need - it only represents calories burned at complete rest, before accounting for any movement, exercise, or daily activity. Multiplying BMR by an activity factor produces Total Daily Energy Expenditure (TDEE), the number that actually reflects how many calories you burn in a typical day. BMR is a useful building block, but using BMR alone as a calorie target would significantly underestimate the needs of anyone who is not completely sedentary.
Why BMR Varies Between Individuals
Muscle tissue burns more calories at rest than fat tissue, which is why two people of the same height, weight, age, and sex can still have different BMRs depending on their body composition. BMR also naturally declines with age, partly due to a gradual, common loss of muscle mass over time - a factor the Mifflin-St Jeor equation accounts for by including age directly in its formula.
How to Use the BMR Calculator
- Open the BMR Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the basal metabolic rate calculator works.
Frequently Asked Questions
How to calculate BMR?
Use the Mifflin-St Jeor equation: BMR = 10 * weight(kg) + 6.25 * height(cm) - 5 * age(years) + s, where s is +5 for men and -161 for women. Enter your details above and this basal metabolic rate calculator runs the formula for you.
How is BMR different from the calories I actually burn in a day?
BMR only counts calories burned at complete rest. Your total daily calories burned (TDEE) also includes movement and exercise, and is calculated by multiplying BMR by an activity factor.
Which BMR formula is more accurate, Mifflin-St Jeor or Harris-Benedict?
Mifflin-St Jeor, developed in 1990, has been shown in multiple studies to be more accurate for most people than the older Harris-Benedict equation, which is why it's now more commonly recommended.
Does muscle mass affect my BMR?
Yes. Muscle tissue burns more calories at rest than fat tissue, so individuals with higher muscle mass tend to have a higher BMR than someone of the same height, weight, and age with less muscle.
Does BMR decrease with age?
Yes, BMR generally declines gradually with age, partly due to a common, gradual loss of muscle mass over time - which is why the Mifflin-St Jeor formula includes age as a direct input.
Should I eat exactly my BMR in calories per day?
No. BMR represents calories burned at complete rest only. Eating only your BMR in calories would create a large deficit for anyone with normal daily activity, since it does not include the calories burned through movement and exercise.
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Last updated: September 27, 2026.