BMR Calculator
Your Basal Metabolic Rate is the number of calories your body burns at complete rest: heart beating, lungs breathing, brain running, body temperature held steady. It is the biggest single piece of your daily burn, usually 60 to 70% of everything you use in a day.
This calculator gives you five peer-reviewed formulas, shows how they compare for your body, and scales your BMR into a full daily estimate. Every number is traceable to the published research at the bottom of the page. Looking for calorie and macro targets instead? That is the job of our TDEE Calculator.
Tell Us About Yourself
Metric (cm, kg)
Imperial (ft, lbs)
Feminine
Masculine
Not sure? Keep the recommended one. They all estimate the same thing, just from slightly different research.
Your Basal Metabolic Rate
calories per day your body burns at complete rest
Mifflin-St Jeor equation (1990)
74 kcal per hour
Burned around the clock, even while you sleep
~86 watts
Your body idles at about the power of an old light bulb
12,463 kcal per week
Your resting burn before a single step
What Happens When You Start Moving
Nobody lives at their BMR. Multiply it by an activity level and you get your Total Daily Energy Expenditure (TDEE), the number your calorie targets are actually built on. Here is your BMR scaled across the standard activity multipliers:
Ready to turn this into calorie and macro targets for losing fat, maintaining, or building muscle?
Get Your Full TDEE & Calorie TargetsHow the Formulas Compare for You
Every equation is an estimate built from lab measurements of real people. If they land within a hundred calories of each other for you, that spread is your realistic margin of error. No calculator beats a few weeks of tracking your weight and food.
Katch-McArdle and Cunningham are hidden because they need your body fat percentage. Add it above to compare all five.
Where Your Resting Calories Actually Go
At complete rest, a handful of organs do almost all the burning. These shares come from direct organ-level measurements [8].
Brain
~20% of your BMR
Roughly 2% of your body weight burning a fifth of your resting calories. Thinking is expensive whether or not it feels like it.
Liver
~20% of your BMR
Your chemical processing plant: filtering blood, storing glycogen, and building proteins around the clock.
Resting Muscle
~20% of your BMR
Even doing nothing, muscle costs calories to maintain. It is the one slice of this pie you can meaningfully grow.
Heart & Kidneys
~15-20% of your BMR
Small organs with enormous per-gram burn rates. Your heart beats about 100,000 times a day and never takes a rest day.
Everything Else
~20-25% of your BMR
Skin, gut, lungs, immune system, fat tissue, and the thousand background processes that keep you alive.
BMR vs RMR vs TDEE
Three numbers that get mixed up constantly. Here is the clean version.
BMR: the lab number
Basal Metabolic Rate is measured under strict conditions: after a full night of sleep, fasted for 12 hours, lying still in a temperature-controlled room. It is the true floor of your energy use, and it is what the formulas on this page estimate [1][2].
RMR: the practical cousin
Resting Metabolic Rate relaxes the lab rules: measured seated or resting, not necessarily fasted. It usually runs about 10% higher than BMR because digestion and light wakefulness sneak in. Most casual uses of "BMR" are really describing RMR [7].
TDEE: the one you eat to
Total Daily Energy Expenditure is your BMR plus movement, exercise, and digestion: everything you burn in a real day. Calorie targets are set against TDEE, never BMR. Get yours with the TDEE Calculator.
What Moves Your BMR (and What Doesn't)
What genuinely moves it
- Lean mass. The single biggest factor: fat-free mass explains most of the difference in BMR between people [9]. More muscle, higher floor.
- Body size. A bigger body has more tissue to keep alive. This is why BMR drops as you lose weight, not because anything is broken.
- Age. BMR drifts down roughly 1 to 2% per decade in adulthood, mostly because lean mass shrinks. Training and protein slow that slide.
- Hormones and genetics. Thyroid hormone level is a measurable contributor [9], and two people with identical stats can still differ by a couple hundred calories.
- Hard dieting. Long, aggressive deficits can suppress BMR beyond what weight loss alone predicts (adaptive thermogenesis), typically in the 5 to 15% range, and it eases when you return to maintenance [10].
What barely moves it
- "Metabolism-boosting" foods. Green tea, chili, ice-cold water: the measured effects exist but are tiny, tens of calories at best. Nothing you can eat meaningfully raises your BMR.
- Meal timing. Eating six small meals versus two big ones does not change your resting burn. Total intake and protein content are what matter.
- "Starvation mode". Eating below your BMR does not stop fat loss or make your body "hold on" to fat. Adaptation is real but modest [10]; the real costs of crash dieting are muscle loss, low energy, and rebound.
- A single workout. The post-exercise "afterburn" is small. Training changes your BMR the slow way: by building muscle you then carry around all day.
How to Use Your BMR
1. Don't eat to it
BMR is a reference point, not a calorie target. It describes a day spent motionless in bed. Plans built on BMR alone undershoot badly and cost you muscle and energy.
2. Scale it to your life
Multiply BMR by an honest activity level to get your TDEE, then set your calories against that. The TDEE Calculator does this and hands you macro targets too.
3. Protect it
Lift weights and eat enough protein, especially in a deficit. Keeping lean mass is how you keep your BMR high while the scale goes down.
Want the bigger picture on daily burn and calorie targets? Read our full TDEE guide or turn your numbers into a plan with Macros 101.