BMR Calculator
The calories your body burns doing nothing at all. Around two thirds of everything you burn in a day starts here.
Don’t know it? Estimate it with the body fat calculator. Leave it blank if you would be guessing, since a bad estimate makes this formula worse rather than better.
Your BMR
1,684 cal/day
Mifflin-St Jeor equation
Mifflin-St Jeor
1,684
Recommended default
Harris-Benedict
1,731
Revised 1984
Katch-McArdle
–
Needs body fat %
Do not eat at this number. BMR is what you burn at complete rest. Your actual daily target is BMR multiplied by an activity factor. The TDEE calculator does that and gives you cut, maintain and bulk figures.
What BMR actually measures
Your body spends energy around the clock whether or not you do anything with it. Your heart pumps, your kidneys filter, your brain fires, damaged cells get replaced, and your temperature stays within a degree of where it should be. That baseline cost is your Basal Metabolic Rate.
In a lab it is measured by indirect calorimetry: you lie still after an overnight fast while a machine reads the oxygen you use and the carbon dioxide you produce. Since most people are not going to do that, we predict it from height, weight, age and sex, which turns out to work reasonably well. For a healthy adult, a good equation lands within about 10% of the measured value.
BMR matters because of its size. At 60 to 70% of daily expenditure, it dwarfs the part you control at the gym. It is also the reason weight loss gets harder as it goes: a lighter body has a smaller baseline, so the same diet buys less progress than it did at the start.
The three equations
Mifflin-St Jeor (1990)
The modern standard, validated against indirect calorimetry and recommended by the Academy of Nutrition and Dietetics. Accurate to within about 10% for most healthy adults.
Men: 10 × kg + 6.25 × cm − 5 × age + 5
Women: 10 × kg + 6.25 × cm − 5 × age − 161
Harris-Benedict (1919, revised 1984)
The original, and still widely quoted. It tends to run about 5% high on modern populations, because the people it was built from differed from the people it now gets applied to.
Men: 13.397 × kg + 4.799 × cm − 5.677 × age + 88.362
Women: 9.247 × kg + 3.098 × cm − 4.330 × age + 447.593
Katch-McArdle
Works from lean mass rather than total weight, which makes it the most accurate of the three when your body fat figure is real. A DEXA scan or a careful caliper reading qualifies. A guess from a bathroom scale does not.
370 + 21.6 × lean mass in kg
Here is the difference it makes. Two people weigh 176 lb. One is at 15% body fat, the other at 30%. Katch-McArdle gives them 1,839 and 1,580 calories, a gap of 259 a day that height and weight alone would never reveal.
What BMR is made of
Resting energy is not spread evenly around the body. Your organs do most of the work, which explains why BMR responds far less to training than people expect.
| Tissue | Share of BMR | Note |
|---|---|---|
| Liver | About 27% | The single largest consumer |
| Brain | About 19% | Constant, regardless of what you are thinking about |
| Skeletal muscle | About 18% | At rest. Far higher when it is working. |
| Kidneys | About 10% | Small organs with a very high metabolic rate |
| Heart | About 7% | Never stops |
| Fat tissue | About 4% | Roughly 2 calories per pound per day |
This is the honest answer to whether lifting transforms your metabolism. A pound of muscle burns about 6 calories a day at rest, against 2 for a pound of fat. Real, but small. The bigger payoff from training is what it does to the rest of your daily burn, and to how much muscle you keep while dieting.
BMR by weight: a rough guide
Calculated with Mifflin-St Jeor at age 30, for two common heights. Use them to sanity-check your own result rather than as a target.
| Man, 5'9" | |
|---|---|
| 130 lb | 1,538 cal |
| 150 lb | 1,629 cal |
| 170 lb | 1,720 cal |
| 190 lb | 1,811 cal |
| 210 lb | 1,901 cal |
| 230 lb | 1,992 cal |
| Woman, 5'4" | |
|---|---|
| 110 lb | 1,207 cal |
| 130 lb | 1,297 cal |
| 150 lb | 1,388 cal |
| 170 lb | 1,479 cal |
| 190 lb | 1,570 cal |
| 210 lb | 1,660 cal |
Every 20 lb adds roughly 90 calories to resting burn. That is also why BMR falls as you lose weight, and why a calorie target set at your starting weight stops working partway through.
What actually changes your BMR
Muscle mass
Raises it, modestly. About 6 calories per pound of muscle per day. Worth doing for a dozen other reasons, but nobody has ever transformed their metabolism this way.
Long or aggressive dieting
Lowers it, by more than your smaller size alone would explain. This is adaptive thermogenesis. Slower fat loss, plenty of protein and continued lifting all keep it to a minimum.
Thyroid function
Thyroid hormone sets the pace of resting metabolism directly. An underactive thyroid can lower BMR meaningfully, and it is one of the few genuine medical explanations for stalled weight loss.
Sleep
Short sleep has only a small effect on resting rate, but it sharply increases hunger and reduces how much you move the next day. The damage shows up in intake and NEAT, not in BMR.
Caffeine, spicy food, cold showers
All raise resting expenditure, and all by amounts too small to matter: typically 30 to 100 calories a day, often less, and the effect fades as you get used to them.