Skip to main content
Simple Calculators

BMR Calculator

Your basal metabolic rate — the calories your body burns at complete rest

Your Details

Related calculators

All health & fitness

Quick summary

Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest just to keep you alive. This calculator uses the Mifflin-St Jeor equation, which the Academy of Nutrition and Dietetics recommends for healthy adults. A 30-year-old, 180 cm, 80 kg man has a BMR of about 1,780 calories a day. To estimate what you burn including activity, multiply BMR by an activity factor in the TDEE calculator.

Reviewed by Simple Calculators TeamLast reviewed

For information only — not medical advice. Results are estimates from published formulas and can't account for your health history. Talk to a doctor or other qualified clinician before making health decisions.

How to use this calculator

  1. Choose your Units: Imperial (lbs, in) or Metric (kg, cm).
  2. Select your Sex, since the Mifflin-St Jeor equation uses a different constant for men (+5) and women (−161).
  3. Enter your Age in years; the calculator accepts 15 to 100.
  4. Enter your Weight and Height in the units you chose (for example, 5 ft 4 in is 64 inches).
  5. Read your Basal Metabolic Rate in calories per day at complete rest. Don't eat to this number; multiply it by an activity factor (use the TDEE calculator) to estimate the calories you actually burn.

BMR Formulas

BMR — Mifflin-St Jeor (Men)

BMR=(10×w)+(6.25×h)−(5×a)+5BMR = (10 \times w) + (6.25 \times h) - (5 \times a) + 5
w
Weight in kilograms (pounds × 0.453592)
h
Height in centimeters (inches × 2.54)
a
Age in years

Worked example

30-year-old man, 80 kg, 180 cm

Given
w = 80 kg
h = 180 cm
a = 30 years
Calculation
BMR=800+1125−150+5BMR = 800 + 1125 - 150 + 5
Result
BMR = 1,780 kcal/day

BMR — Mifflin-St Jeor (Women)

BMR=(10×w)+(6.25×h)−(5×a)−161BMR = (10 \times w) + (6.25 \times h) - (5 \times a) - 161
w
Weight in kilograms (pounds × 0.453592)
h
Height in centimeters (inches × 2.54)
a
Age in years

Worked example

35-year-old woman, 150 lb (68.04 kg), 64 in (162.56 cm)

Given
w = 68.04 kg
h = 162.56 cm
a = 35 years
Calculation
BMR=680.388+1016−175−161=1360.388BMR = 680.388 + 1016 - 175 - 161 = 1360.388
Result
BMR ≈ 1,360 kcal/day

Frequently asked questions

What is BMR?

Basal metabolic rate is the number of calories your body needs at complete rest to keep essential functions going — breathing, circulation, cell repair, brain activity. For most people it's the largest part of daily energy use, typically around 60–70%. Everything you do on top of resting, from walking to exercise to digesting food, adds to it.

How is BMR calculated?

This calculator uses the Mifflin-St Jeor equation: for men, BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5; for women, the same but − 161 instead of + 5. It's regarded as the most accurate of the common formulas for healthy adults. If you enter imperial units, it converts pounds to kilograms and inches to centimeters first, then rounds to the nearest calorie.

What is a normal BMR?

There is no single normal BMR, because it depends on your size, age, and sex. Larger and younger people burn more at rest, and men usually have a higher BMR than women of the same size. As examples from this calculator, a 30-year-old man at 80 kg and 180 cm has a BMR of about 1,780 calories, and a 35-year-old woman at 150 lb and 5 ft 4 in has about 1,360.

What's the difference between BMR and TDEE?

BMR is calories burned at rest, while TDEE (total daily energy expenditure) is BMR multiplied by an activity factor to include movement and exercise. TDEE is the number you'd actually eat to maintain weight. BMR is the foundation; TDEE is what you use for diet planning. Use our TDEE calculator, which applies factors from 1.2 (sedentary) to 1.9 (extra active).

Does BMR go down with age?

Yes, estimated BMR goes down as you age. In the Mifflin-St Jeor equation, each extra year of age lowers BMR by 5 calories a day, so ten years reduces it by 50 calories if your weight and height stay the same. In real life, loss of muscle with age is a big part of the decline, which is why strength training is often recommended for healthy aging.

How accurate is a BMR calculator?

A BMR calculator gives a good estimate for most healthy adults, but it is not a measurement. The equation uses only weight, height, age, and sex, so it cannot account for muscle mass, genetics, thyroid conditions, or medications. Very muscular people may be underestimated. A clinician can measure resting metabolic rate directly with indirect calorimetry if you need a precise number.

Why does BMR matter for weight loss?

BMR matters because it sets your baseline calorie burn and anchors any calorie target. Knowing your BMR (and TDEE) lets you set a sensible deficit for fat loss without eating too little. As a general guide, most adults shouldn't eat below their BMR for extended periods without medical supervision; talk to a doctor or registered dietitian before starting a very low-calorie diet.

Key terms

BMR
Basal metabolic rate — calories burned at complete rest.
Mifflin-St Jeor
The equation used here, considered most accurate for healthy adults.
TDEE
BMR × activity factor — total calories burned in a day.

Methodology, sources & limitations

This page shows the formula, assumptions, and limitations used for this estimate. Rates, thresholds, and other time-sensitive inputs can change, so verify them against the relevant official source before relying on a result.

For our review approach and the primary sources we consult, see the methodology and source policy. If you spot an outdated figure or formula, please contact us with a correction.