Your basal metabolic rate, or BMR, is the number of calories your body burns just to stay alive: breathing, keeping your heart beating, maintaining body temperature, and running the basic chemistry of your cells. Knowing it is the starting point for almost every calorie target, from weight loss to muscle gain. The good news is that you do not need a lab test to estimate it. With one equation, a pencil, and about two minutes, you can calculate your BMR by hand to within a useful range.
If you want the answer instantly, use our free BMR calculator and then come back here to see exactly how the number is produced. This guide walks through the Mifflin-St Jeor equation, the formula researchers and dietitians use most often, with two fully worked examples: one for a man and one for a woman, both starting from pounds and feet/inches, the units most readers in the United States use every day.
BMR is the energy your body needs at complete rest in a neutral environment, after fasting, just to keep you alive. It does not include the calories you burn walking to work, exercising, digesting food, or even fidgeting at your desk. Think of it as the idle fuel consumption of your body: the baseline burn that happens whether you spend the day on the couch or on your feet.
For most adults, BMR accounts for roughly 60 to 70 percent of total daily calorie burn. The rest comes from physical activity and the thermic effect of food, which is the energy cost of digesting what you eat. That is why BMR is so useful. Once you know your baseline, you can add activity on top of it to estimate your total daily energy expenditure, or TDEE, and from there set a calorie target for losing, maintaining, or gaining weight.
It helps to keep BMR separate from resting metabolic rate, or RMR. The two are close cousins and the numbers are usually within a few percent of each other, but they are not identical. RMR is measured under less strict conditions and includes a small amount of light activity, so it typically runs slightly higher than BMR. Most online calculators, including ours, report a BMR estimate based on the Mifflin-St Jeor equation, and the difference between BMR and RMR rarely changes the practical advice that follows from the number.
Several equations exist for estimating BMR. The best known are the Harris-Benedict equation, first published in 1919 and later revised, and the Mifflin-St Jeor equation, published in 1990. When researchers compared the leading formulas against measurements from indirect calorimetry, the Mifflin-St Jeor equation came out most accurate for the general adult population, typically landing within about 10 percent of measured values. That is why dietitians, fitness professionals, and most modern calculators use it as the default.
The equation has separate versions for men and women, because sex differences in body composition affect baseline energy needs at the same height and weight. You need three inputs: your weight, your height, and your age. The equation uses metric units, so if you weigh yourself in pounds and measure height in feet and inches, you will convert first. The conversions are simple and are shown in full below.
Mifflin-St Jeor equation
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
The result is your estimated BMR in calories (kcal) per day.
Notice the structure. Each kilogram of body weight adds 10 calories. Each centimeter of height adds 6.25 calories. Each year of age subtracts 5 calories, which reflects the slow decline in metabolic rate as we get older. Men add 5 calories at the end; women subtract 161. That final adjustment is the only place the two formulas differ, and it accounts for average differences in muscle mass and body composition.
The Mifflin-St Jeor equation only works with metric inputs. If you put pounds and inches straight into the formula, the answer will be badly wrong, so conversion is the first step, not an optional extra. You need two conversion factors:
| Conversion | Formula | Example |
|---|---|---|
| Pounds to kilograms | Weight in kg = weight in lb ÷ 2.205 | 190 lb ÷ 2.205 = 86.2 kg |
| Feet and inches to centimeters | Height in cm = total inches × 2.54 | 5 ft 10 in = 70 in × 2.54 = 177.8 cm |
| Inches to centimeters | Height in cm = inches × 2.54 | 65 in × 2.54 = 165.1 cm |
To turn feet and inches into total inches, multiply the feet by 12 and add the remaining inches. A person who is 5 ft 10 in is 70 inches tall (5 × 12 + 10 = 70). A person who is 5 ft 5 in is 65 inches tall (5 × 12 + 5 = 65). Then multiply by 2.54 to get centimeters. Rounding to the nearest whole centimeter is fine; it changes the final BMR by only a few calories.
The same applies to weight. Dividing pounds by 2.205 gives kilograms. Rounding to one decimal place is plenty precise for this purpose. A small rounding difference in weight shifts the final answer by only a handful of calories, far less than the natural day-to-day variation in your actual metabolic rate.
Meet our first example: a 35-year-old man who weighs 190 lb (86.2 kg) and stands 5 ft 10 in (178 cm) tall. Here is the full calculation, step by step, using the men's formula.
Inputs: weight 86.2 kg, height 178 cm, age 35
Formula: BMR = 10 × 86.2 + 6.25 × 178 − 5 × 35 + 5
Step by step:
10 × 86.2 = 862
6.25 × 178 = 1,112.5
5 × 35 = 175
862 + 1,112.5 − 175 + 5 = 1,804.5
Result: BMR ≈ 1,805 calories per day.
Check the logic: the weight term contributes 862 calories, the height term contributes 1,112.5 calories, aging subtracts 175 calories, and the male adjustment adds 5. The total, 1,804.5, rounds to about 1,805 calories per day. That is the energy this man would burn in a day of complete rest. In real life he burns more, because he moves, works, and digests food, so his total daily burn will be higher. How much higher depends on his activity level, which we cover near the end of this guide.
It is worth pausing on what this number does and does not mean. It does not mean he must eat exactly 1,805 calories. It means his body needs roughly that much before any activity at all. Eating well below BMR for a long stretch is generally not advisable, because it can leave too little energy for basic functions and make a diet hard to sustain. BMR is a floor for planning, not a target to eat at.
Now a second example: a 30-year-old woman who weighs 150 lb (68.0 kg) and stands 5 ft 5 in (165 cm) tall. This time we use the women's formula, which ends with minus 161 instead of plus 5.
Inputs: weight 68.0 kg, height 165 cm, age 30
Formula: BMR = 10 × 68.0 + 6.25 × 165 − 5 × 30 − 161
Step by step:
10 × 68.0 = 680
6.25 × 165 = 1,031.25
5 × 30 = 150
680 + 1,031.25 − 150 − 161 = 1,400.25
Result: BMR ≈ 1,400 calories per day.
Again, check the arithmetic. The weight term gives 680 calories, the height term gives 1,031.25 calories, aging subtracts 150, and the female adjustment subtracts 161. The total is 1,400.25, which rounds to about 1,400 calories per day. Two people of different sex, size, and age get meaningfully different baselines, which is exactly why a one-size-fits-all calorie number, such as a generic 2,000-calorie diet, fits almost nobody precisely.
Try the same calculation with your own numbers. Write down your weight in kilograms, your height in centimeters, and your age, then work through the four terms one at a time. If you would rather skip the arithmetic, our BMR calculator runs the identical equation and shows your result instantly, along with your estimated TDEE at several activity levels.
Most wrong answers come from one of a handful of slips, not from the equation itself. Watch for these:
Forgetting to convert units. This is the most common error by far. Plugging 190 lb and 70 inches directly into a formula that expects kilograms and centimeters produces a number in the thousands of calories too high. Always convert first: pounds divided by 2.205, inches multiplied by 2.54.
Using the wrong formula for your sex. The male and female versions differ by 166 calories at the final step (+5 versus −161). Using the wrong one shifts your estimate by that full amount, which is enough to throw off a weight-loss target.
Mixing up height in feet with height in inches. Entering 5.10 for 5 ft 10 in, as if it were a decimal, is a classic slip. Convert to total inches first (70 in), then to centimeters (178 cm). The decimal form 5.10 feet is not a real height.
Rounding too early. Rounding each intermediate term to a round number before adding them up can push the answer off by 10 to 20 calories. Keep one decimal place through the working, and round only the final result.
Treating BMR as total daily burn. BMR is the resting baseline only. Your actual daily burn is higher, because you move, work, exercise, and digest food. If you set your calorie intake equal to your BMR and you are active, you will be in a deficit without realizing it. The next section shows how to go from BMR to your full daily total.
To turn BMR into total daily energy expenditure (TDEE), multiply it by an activity factor that reflects how much you move on a typical day. These multipliers are standard in nutrition practice:
| Activity level | Multiplier | What it means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little or no exercise |
| Lightly active | 1.375 | Light exercise or sports 1 to 3 days a week |
| Moderately active | 1.55 | Moderate exercise or sports 3 to 5 days a week |
| Very active | 1.725 | Hard exercise or sports 6 to 7 days a week |
| Extra active | 1.9 | Very hard exercise, physical job, or twice-daily training |
Take the man from the first example, with a BMR of about 1,805 calories. If he exercises moderately three to five days a week, his multiplier is 1.55:
TDEE = BMR × activity multiplier
1,805 × 1.55 = 2,797.75 ≈ 2,798 calories per day
That is his estimated total daily burn. Eating about 2,798 calories a day would roughly maintain his weight. Eating less would create a deficit for weight loss; eating more would create a surplus for weight gain.
Be honest about your activity level. Most people overestimate it, which inflates TDEE and makes a weight-loss plan stall. If you sit most of the day and work out twice a week, lightly active (1.375) is the honest choice, not moderately active. When in doubt, pick the lower multiplier, track your weight for two to three weeks, and adjust based on what actually happens rather than what the formula predicted.
Once you know your BMR and TDEE, you can set a calorie target with a clear purpose. For weight loss, a common approach is to eat 300 to 500 calories below TDEE, which produces a steady loss of roughly 0.5 to 1 lb (0.2 to 0.5 kg) per week. Our calorie deficit calculator works out the exact deficit for your goal, and our TDEE calculator gives you the full activity breakdown in one place.
For maintaining weight, aim to eat close to TDEE. For gaining muscle, a modest surplus of 200 to 300 calories above TDEE, combined with resistance training and enough protein, is a sensible starting point. In all three cases, recalculate every few months or after a weight change of 10 lb (4.5 kg) or more, because a smaller body burns fewer calories at rest, and your BMR will drift down as you lose weight.
Remember that any BMR equation is an estimate. It does not account for muscle mass directly, so two people with the same height, weight, age, and sex can have different true BMRs if one is much more muscular. People with a great deal of muscle may burn more than the equation predicts; people with very low muscle mass may burn less. Use the number as a well-grounded starting point, track real results for two to three weeks, and adjust your intake based on the trend on the scale and how you feel.
Disclaimer: This article is for general information only and is not medical advice. BMR equations are estimates and individual needs vary. Talk to your doctor or a registered dietitian before changing your diet or exercise routine, especially if you have a medical condition or are taking medication.
Written by the Live Fitness Check editorial team · Reviewed against our calculator methodology · Last updated October 2026
