Macrition Macrition
Metabolism

BMR Calculator

Calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor and Harris-Benedict equations. Free BMR calculator with daily burn breakdown.

BMR at a glance

Rather than a population average, the BMR below personalizes it - your age, weight, height and sex feed the Mifflin-St Jeor equation, the same one the reference ranges are built from.

Calculate your Basal Metabolic Rate (BMR) using the Mifflin-St Jeor and Harris-Benedict equations. Free BMR calculator with daily burn breakdown.

Calculate your BMR

Your Basal Metabolic Rate is the calories your body burns at complete rest.

years

Your basal metabolic rate

,
Mifflin-St Jeor
,
Harris-Benedict (rev. 1984)
,
Average
,
Est. daily burn (×1.4)

Your BMR is the calories your body burns at rest. To find maintenance calories (TDEE), multiply by your activity factor - the "Est. daily burn" figure above assumes light everyday activity (a ×1.4 multiplier between the sedentary and light-exercise factors).

Understanding Basal Metabolic Rate

Your Basal Metabolic Rate (BMR) is the number of calories your body would burn if you stayed in bed all day doing absolutely nothing. It represents the energy required to keep your heart beating, lungs breathing, brain firing, and cells maintaining themselves. For most people, BMR accounts for 60-75% of total daily energy expenditure.

The science behind BMR formulas

The most widely recommended equation is the Mifflin-St Jeor equation (1990), which the American Dietetic Association found to be the most accurate predictive formula for healthy adults, with an average error of about 10% versus indirect calorimetry.

Why BMR matters for your goals

Knowing your BMR is the foundation of any data-driven nutrition plan. If your goal is fat loss, you need to consume fewer calories than your TDEE, and TDEE is calculated by multiplying BMR by an activity factor. Without an accurate BMR estimate, you're flying blind.

Editorial and formula review
Formulas verified against published peer-reviewed sources Last verified

Formula sources, population limits, and references for this metabolism calculator are documented in our public methodology. Read the methodology · Medical disclaimer

Frequently asked questions

For adult women, BMR typically ranges from 1,200 to 1,600 kcal/day. For adult men, 1,500 to 2,000 kcal/day.
The Mifflin-St Jeor equation is currently considered the most accurate predictive formula for healthy adults, with an average error of about 10%.
Eating below BMR is generally not recommended because it can trigger muscle loss, hormonal disruption, and metabolic adaptation.
Yes. As you lose weight, BMR decreases because there is less tissue to maintain. Building muscle can partially offset this decline.
BMR is measured under strict laboratory conditions. RMR (Resting Metabolic Rate) is measured under less controlled conditions and is typically 10% higher.