BMR Calculator

Calculate your basal metabolic rate with Mifflin–St Jeor, Harris–Benedict or Katch–McArdle.

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Units

Sex

Age

years

Height

Height (feet)

Inches

Weight

Formula

Body fat

Enter your values to see the result.

These results are estimates for general information, not medical advice. Body shape, muscle mass, age, ethnicity and health conditions all affect what is right for you, so talk to a doctor or dietitian before making health decisions.

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How this calculation works

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Formula: Mifflin–St Jeor: 10W + 6.25H − 5A + S (S = 5 for men, −161 for women). Revised Harris–Benedict: men 88.362 + 13.397W + 4.799H − 5.677A; women 447.593 + 9.247W + 3.098H − 4.330A. Katch–McArdle: 370 + 21.6W(1 − F/100). Daily expenditure = BMR × activity factor.
Variables: W = weight in kg
H = height in cm
A = age in years
F = body fat percentage
Activity factor = 1.2, 1.375, 1.55, 1.725 or 1.9
Units: Imperial inputs are converted to kg and cm.
Energy: kcal/day
Example: A 30-year-old man who is 175 cm tall and weighs 70 kg has a BMR of about 1,649 kcal with Mifflin–St Jeor: 10 × 70 + 6.25 × 175 − 5 × 30 + 5. If he exercises 3–5 days a week, multiply by 1.55 to get about 2,556 kcal a day.
Assumptions: These results are estimates for general information, not medical advice. Body shape, muscle mass, age, ethnicity and health conditions all affect what is right for you, so talk to a doctor or dietitian before making health decisions.
Source: ToolzHive calculation guide and calculator implementation. External reference verification is pending.
Last reviewed: October 3, 2026 Implementation review; specialist review has not been recorded.

Methodology & References

The method depends on the selected model and input options. Review the assumptions and references above before interpreting the result.

Choose metric or imperial units, then enter your sex, age, height and weight.
Pick a formula. Keep Mifflin–St Jeor unless you know your body fat percentage, in which case Katch–McArdle can be more accurate.
Read your BMR and the table of daily calories for each activity level. Use the row that matches your week.

Interpretation and limitations

What is the difference between BMR and TDEE? BMR is the energy you use at complete rest. TDEE (total daily energy expenditure) adds everything else: walking, exercise, work and digesting food. TDEE is the number to use when planning how much to eat.
Which BMR formula is most accurate? For most adults, Mifflin–St Jeor is the most accurate of the common equations, usually within about 10% of measured values. Katch–McArdle can be better for lean or very muscular people because it uses lean body mass.
Why is my BMR lower than I expected? BMR falls with age and with lower muscle mass, and women usually have lower BMRs than men of the same size. Remember it is only your resting burn; your real daily needs are higher.

References

External reference verification is pending. The formula and examples describe the current ToolzHive implementation.

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How to use the BMR Calculator

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest just to keep you alive: breathing, circulating blood and keeping warm. This calculator uses the Mifflin–St Jeor equation, which research has found to be the most accurate everyday formula, and also offers the revised Harris–Benedict and Katch–McArdle equations. It then multiplies your BMR by five activity levels to estimate the calories you burn in a normal day (your TDEE).

1 Choose metric or imperial units, then enter your sex, age, height and weight.
2 Pick a formula. Keep Mifflin–St Jeor unless you know your body fat percentage, in which case Katch–McArdle can be more accurate.
3 Read your BMR and the table of daily calories for each activity level. Use the row that matches your week.

Example and practical tips

A 30-year-old man who is 175 cm tall and weighs 70 kg has a BMR of about 1,649 kcal with Mifflin–St Jeor: 10 × 70 + 6.25 × 175 − 5 × 30 + 5. If he exercises 3–5 days a week, multiply by 1.55 to get about 2,556 kcal a day.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is the energy you use at complete rest. TDEE (total daily energy expenditure) adds everything else: walking, exercise, work and digesting food. TDEE is the number to use when planning how much to eat.

Which BMR formula is most accurate?

For most adults, Mifflin–St Jeor is the most accurate of the common equations, usually within about 10% of measured values. Katch–McArdle can be better for lean or very muscular people because it uses lean body mass.

Why is my BMR lower than I expected?

BMR falls with age and with lower muscle mass, and women usually have lower BMRs than men of the same size. Remember it is only your resting burn; your real daily needs are higher.

How to Use BMR Calculator
Calculate your basal metabolic rate (BMR) with the Mifflin–St Jeor, Harris–Benedict or Katch–McArdle formula, plus daily calories by activity level.