BMR Calculator
Calculate your basal metabolic rate, the calories your body burns at complete rest. Uses Mifflin-St Jeor by default, with Katch-McArdle available if you know your body fat percentage.
Enter your details above to see your BMR.
What is BMR?
BMR, basal metabolic rate, is the number of calories your body burns just keeping you alive. Breathing, pumping blood, maintaining body temperature, running your brain, replacing cells. It is the floor of your daily energy expenditure, the baseline you would burn if you stayed in bed all day.
For most adults, BMR accounts for 60 to 70 percent of total daily calorie burn. The rest comes from digestion, daily movement, and exercise. Understanding your BMR is the starting point for building any calorie target, whether you want to cut, bulk, or maintain.
Mifflin-St Jeor vs Katch-McArdle
Mifflin-St Jeor (default)
Uses weight, height, age, and gender. Does not need body fat percentage, which is why most calculators default to it. Accurate within about 10 percent for people in a normal body composition range.
Katch-McArdle
Uses lean body mass directly, calculated from weight and body fat percentage. More accurate for people who are notably leaner or more muscular than average, because muscle and fat burn different amounts at rest. Requires a body fat estimate.
Which to use
If you do not know your body fat, use Mifflin-St Jeor. If you have a recent DEXA or InBody reading, use Katch-McArdle. For most people the two results fall within 5 percent of each other.
Body Weight Methodology
BMR changes when body composition changes. FitCommit reads weight alongside BMI, healthy-weight ranges, ideal-weight formulas, body fat percentage, and lean mass before turning the number into a calorie or macro target.
Read the body weight methodologyBMR vs TDEE vs Active Calories
These three terms get mixed up constantly. They are not the same thing.
- •BMR: calories at complete rest. What you burn doing nothing.
- •TDEE: total daily energy expenditure. BMR plus digestion, movement, and exercise. This is your maintenance calorie level.
- •Active calories: what your watch shows during a workout. Only the calories burned from that activity, on top of what you would have burned at rest.
When you plan calories for fat loss or muscle gain, you work off TDEE, not BMR. Eating at BMR would be a severe deficit for most people and is not sustainable.
Reviewed by Andrew Menechian, Head of Fitness, FitCommit
Andrew reviews FitCommit's calorie, macro, and body-composition methodology. His background includes 12+ years in fitness, PN1, PNC 1&2, Poliquin PICP 1&2, bodybuilding, powerlifting, and coaching education.
Frequently Asked Questions
What is BMR?
BMR is basal metabolic rate, the number of calories your body burns at complete rest to keep organs running, maintain temperature, and support basic cell function. It accounts for roughly 60 to 70 percent of your total daily calorie burn. BMR is measured under lab conditions (fasted, lying still, thermoneutral room). What calculators give you is an estimate based on your body stats.
Is my BMR too low?
Most calculated BMRs fall in the 1,300 to 2,000 calorie range for adults. If yours feels low, the usual cause is low lean mass, not a broken metabolism. True metabolic disorders are rare and diagnosed by a doctor. Before assuming your BMR is low, check whether you are actually eating at the level you think you are. Food tracking accuracy is the most common blind spot.
What is the difference between BMR and metabolism?
Metabolism is an umbrella term for all calorie-burning processes in your body. BMR is one piece of that, the baseline you burn at rest. Metabolism also includes the thermic effect of food (digestion), non-exercise activity thermogenesis (NEAT, like fidgeting and walking), and exercise. When people say metabolism, they usually mean total daily energy expenditure (TDEE), not BMR.
How do I increase my BMR?
The reliable lever is adding lean muscle mass. Each pound of muscle burns roughly 6 calories a day at rest, which sounds small but compounds. Strength training 3 to 4 times a week and eating enough protein (0.8 to 1.0g per pound of body weight) is the proven path. Supplements, cold plunges, and fasted cardio do not move BMR meaningfully.
How accurate are BMR calculators?
Mifflin-St Jeor is accurate within about 10 percent for most people in a normal body composition range. If you have an unusual build (very muscular, very lean, very high body fat), Katch-McArdle using your body fat percentage is more accurate because it uses lean mass directly. For precise numbers, indirect calorimetry in a lab is the gold standard but costs hundreds of dollars.
Does BMR decrease with age?
Yes, but less than people think. BMR drops roughly 1 to 2 percent per decade after age 20. Most of the apparent slowdown is loss of muscle mass and reduced daily activity, not the BMR itself. Older adults who maintain lean mass and stay active have BMRs close to younger adults of the same size.
Does muscle really burn more calories than fat at rest?
Yes, but the margin is smaller than gym folklore suggests. Muscle burns about 6 calories per pound per day at rest. Fat burns about 2 calories per pound per day. Adding 10 pounds of muscle means roughly 60 extra calories burned at rest daily, not hundreds. The bigger benefit of muscle is what it lets you do in training and daily life, not resting calorie burn.
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