BMR Calculator
Find out how many calories your body burns at complete rest each day, and see how that changes across different activity levels.
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BMR only accounts for calories burned at rest. The table above adds an activity factor to estimate your total daily calorie needs (TDEE) for maintaining your current weight.
How BMR Is Calculated
Basal Metabolic Rate (BMR) is the number of calories your body needs to perform basic life-sustaining functions — breathing, circulation, cell production — while completely at rest. This calculator offers two well-established formulas.
Both formulas use weight, height, and age, since these are the strongest predictors of resting metabolism. The Mifflin–St Jeor equation, published in 1990, is generally considered more accurate for modern populations than the older Harris–Benedict formula.
Frequently Asked Questions
What exactly does BMR measure?
BMR is the energy your body needs just to keep essential functions running — heartbeat, breathing, brain activity, and cell repair — while lying still and not digesting food. It typically makes up 60–75% of the calories you burn in a day.
Why does BMR decrease with age?
As people age, they typically lose lean muscle mass and gain fat mass, and muscle burns more calories at rest than fat does. Hormonal changes also play a role, which is why calorie needs generally decline gradually over the years.
Should I eat exactly my BMR in calories?
No — eating only your BMR would mean eating far less than you actually burn in a day, since it doesn’t include movement or exercise. Use the activity-level numbers in the results above instead; they reflect your real daily calorie needs.
Which formula should I use, Mifflin–St Jeor or Harris–Benedict?
Mifflin–St Jeor is generally recommended, as research has shown it to be more accurate for most people compared to the original Harris–Benedict formula from 1919. We include the revised Harris–Benedict version for comparison, since some people still prefer it.