BMR Calculator
Compare your basal metabolic rate (BMR) across three formulas, then get your daily calorie burn (TDEE), calorie targets by goal, a carb, protein and fat split, and an estimated time to reach your goal weight.
How does your metabolism compare?
BMR by formula
| Formula | BMR | vs. main formula |
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The Katch-McArdle formula is calculated once you enter your body fat %.
Daily calories by activity level
| Activity level | Calories burned per day |
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Bar length shows daily calories burned (TDEE) at each activity level. The orange dashed line marks your BMR, and the orange bar is the activity level you selected.
Daily calories by goal
| Goal | Calories per day | Estimated weekly change |
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Targets apply roughly 10–20% to your TDEE. Weekly change assumes about 7,700 kcal per kg of body fat (about 3,500 kcal per pound).
Carbs, protein and fat for your calorie target
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How BMR changes with age
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BMR is an estimate that varies with age, sex, body composition and genetics. These results are for reference only; for personal medical or nutrition advice, ask a qualified professional.
How to use
How BMR and daily calories are calculated
Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest just to keep you alive: breathing, circulating blood, running your brain and repairing cells. It usually accounts for 60 to 70 percent of the calories you burn in a day. This calculator estimates BMR with three well-known equations, multiplies it by an activity factor to get your total daily energy expenditure (TDEE), and then shows calorie targets for losing, maintaining or gaining weight, a protein-carb-fat split for the target you choose, and an estimate of how long it will take to reach a goal weight. You can type metric values, or use the US units box to enter feet, inches and pounds.
The three formulas
The Mifflin-St Jeor equation, published in 1990, is the default because it is considered the most reliable of the common equations for healthy adults. It is the one the Academy of Nutrition and Dietetics recommends for estimating resting energy needs. With weight in kilograms, height in centimeters and age in years:
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5 | Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
The Harris-Benedict equation dates from 1919 and was revised in 1984. It is shown for comparison because many older calorie charts and books still use it. The Katch-McArdle formula works differently: it ignores age and sex and uses lean body mass, which is your weight minus your body fat. That makes it the best choice if you know your body-fat percentage from a scan or a reliable measurement, particularly for lean or muscular people. Enter your body fat and the comparison table fills in all three results side by side.
Worked example: a 30-year-old woman who is 5 ft 5 in (165 cm) and 140 lb (63.5 kg) gets 10 × 63.5 + 6.25 × 165 − 5 × 30 − 161 = 1,355 kcal per day by Mifflin-St Jeor. A 35-year-old man who is 5 ft 10 in (178 cm) and 180 lb (81.6 kg) gets 10 × 81.6 + 6.25 × 178 − 5 × 35 + 5 = about 1,759 kcal.
From BMR to TDEE
Nobody lies still all day, so BMR is multiplied by an activity factor to estimate TDEE. The calculator uses the standard factors: 1.2 for sedentary, 1.375 for light exercise one to three days a week, 1.55 for moderate exercise three to five days a week, 1.725 for hard exercise six or seven days a week and 1.9 for a very physical job or two workouts a day. People tend to overestimate their activity, so if you are unsure, choose the lower level and adjust after a few weeks of real-world results. The woman in the example above, moderately active, burns about 1,355 × 1.55 = 2,100 kcal per day.
Calorie targets and the 7,700 rule
The goal options apply a percentage to TDEE: about 20 percent below for fast weight loss, 10 percent below for gradual loss, no change to maintain, and 10 or 20 percent above for a lean bulk or weight gain. Weekly change is estimated with the familiar rule of thumb that one kilogram of body fat holds roughly 7,700 kcal (about 3,500 kcal per pound). Real results vary, because your body adapts as weight changes, which is why the time-to-goal estimate suggests recalculating every four to six weeks. A common safe pace is 0.5 to 1 percent of body weight per week. The calculator warns you when a target falls below your BMR or changes your weight faster than that.
Macros: carbs, protein and fat
The balanced split gives 55 percent of calories to carbohydrate, 20 percent to protein and 25 percent to fat, inside the ranges in the US Dietary Guidelines (carbohydrate 45 to 65 percent, protein 10 to 35 percent, fat 20 to 35 percent). The high-protein option moves to 40/30/30 for people who want to protect muscle, and the low-carb option to 30/30/40, which is outside the usual ranges, so it is best discussed with a professional first. Calories per gram are 4 for carbohydrate and protein and 9 for fat. The recommended dietary allowance for protein is 0.8 g per kilogram of body weight, and sports nutrition guidance for active people is typically 1.2 to 2.0 g per kilogram.
How accurate is a BMR estimate?
Equations are averages. For most healthy adults they land within about 10 percent of measured resting energy use, but individual metabolism varies with muscle mass, genetics, hormones, sleep, medications and recent dieting. The best way to use the numbers is as a starting point: eat near your target for two to three weeks, track your weight, and adjust by 100 to 200 kcal if the scale is not moving the way you intended. Do not use the results for medical decisions. Very low calorie diets, pregnancy, breastfeeding, eating disorders and chronic conditions all call for guidance from a doctor or registered dietitian.
Why BMR falls with age
The age term in the Mifflin-St Jeor equation subtracts 5 kcal for every year, so BMR drops by about 50 kcal per decade even if your weight does not change. In real life the drop is often larger because muscle mass declines with age unless you do resistance training. The chart below the results shows your own curve.
Frequently asked questions
What is the difference between BMR and RMR?
BMR is measured under strict conditions: fasted, rested and in a warm, quiet room. Resting metabolic rate (RMR) is measured under looser conditions and is usually slightly higher. The two are close enough that people use the terms interchangeably, and the equations here estimate either.
What is TDEE, and which number should I eat to?
TDEE is your total daily energy expenditure: BMR plus the calories you burn moving, exercising and digesting food. Eating at TDEE keeps your weight stable. Eat below it to lose weight and above it to gain. The calorie target in the results already applies your chosen goal to TDEE.
Which formula should I choose?
Use Mifflin-St Jeor unless you know your body-fat percentage. If you do, add it and compare Katch-McArdle, which can be more accurate for people who are very lean or very muscular. Harris-Benedict is included mainly for comparison with older charts.
Is it safe to eat below my BMR?
Eating below BMR for a long time is not recommended without medical supervision. It can cost muscle, lower energy and slow your metabolism. The calculator shows a warning when a target falls below your BMR; choose a smaller deficit or add activity instead.
How many calories should I cut to lose a pound a week?
A pound of fat holds about 3,500 kcal, so a daily deficit of about 500 kcal gives roughly a pound per week in theory. In practice the pace slows as you lose weight. Aim for steady progress of about 0.5 to 1 percent of body weight per week.
Does the calculator work in pounds?
Yes. Use the US units box to enter feet, inches and pounds, and the metric fields fill in automatically. The results show calories, and the goal timeline works in kilograms with the weight conversions shown in the boxes above.
Is my information stored?
No. Everything is calculated in your browser. Nothing you enter is saved or sent to a server.