BMR Calculator
Estimate the calories your body burns doing nothing but keeping you alive, using the Mifflin-St Jeor equation from the 1990 study that replaced Harris-Benedict as the clinical standard.
Members: the Phorme app recalculates this automatically as you log.
The energy cost of staying alive.
Basal metabolic rate is what your body burns lying still: heartbeat, breathing, brain activity, cell repair, temperature regulation. For most adults it is 60 to 70 percent of everything burned in a day, which is why it anchors every calorie calculation.
We use the Mifflin-St Jeor equation, published by Mifflin and St Jeor in 1990. In head-to-head validation work it predicted measured resting metabolic rate more accurately than the 1919 Harris-Benedict equation, and the Academy of Nutrition and Dietetics now recommends it for healthy adults.
The equation takes weight, height, age, and sex. It reads slightly low for very muscular people and slightly high at higher body fat levels, because lean tissue burns more at rest than fat tissue. Treat the output as a calibrated starting point, not a lab measurement.
- 1. Enter your age, sex, height, and weight.
- 2. Press Calculate to get your basal metabolic rate in calories per day.
- 3. Use the TDEE calculator next to layer your activity level on top of this baseline.
- 4. Recalculate after your body weight changes by more than 5 pounds.
Men: BMR = 10 x weight (kg) + 6.25 x height (cm) minus 5 x age + 5 (Mifflin-St Jeor, 1990).
Women: BMR = 10 x weight (kg) + 6.25 x height (cm) minus 5 x age minus 161 (Mifflin-St Jeor, 1990).
Questions we hear a lot.
What exactly does BMR measure?
BMR is the energy your body spends at rest on baseline function: brain, heart, breathing, cell turnover, temperature regulation. It excludes digestion and all movement. For most people it accounts for roughly 60 to 70 percent of the calories burned in a day.
Why Mifflin-St Jeor instead of Harris-Benedict?
Harris-Benedict dates to 1919 and tends to read high against modern populations. Mifflin-St Jeor, published in 1990, predicted measured resting metabolic rate more accurately in comparison studies, which is why the Academy of Nutrition and Dietetics recommends it for healthy adults.
Can I eat at my BMR to lose weight?
You can, but you rarely need to. Actual maintenance is BMR times an activity factor, so eating at BMR is often an aggressive 20 to 40 percent deficit without you choosing it. Set the deficit off TDEE instead so the size of the cut is deliberate.
Does muscle mass change BMR?
Yes. Lean tissue burns more energy at rest than fat tissue, which is one reason two people at the same body weight can have different BMRs. Mifflin-St Jeor approximates this through weight, height, age, and sex; if you know your lean mass, the Katch-McArdle formula can refine the estimate.
Is a slow metabolism the reason a diet stalls?
Rarely. Measured BMRs usually land within about 10 percent of prediction, and true clinical outliers are uncommon. Most stalls trace to underestimated intake or overestimated activity, both of which sit on top of BMR rather than inside it.
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