What Is BMR? How to Calculate Your Basal Metabolic Rate and What a Normal Number Looks Like

Your BMR is the number of calories your body burns just to stay alive. Lie in bed all day, awake but completely still, and that is what you would use: the cost of your heart beating, your lungs working, your brain running, and your body holding its temperature. For most adults it is the biggest single piece of the calories they burn, usually 60 to 70 percent of the day’s total, and almost nobody knows their own number.

This guide explains what BMR means in plain terms, how to calculate yours in two minutes with a worked example, what a normal BMR looks like by age and sex, how it differs from RMR and TDEE, and the questions people actually ask once they have the number: whether to eat it, whether 1,400 or 1,500 is good, and whether you can raise it.

What does BMR mean?

BMR stands for basal metabolic rate. “Basal” means baseline, and “metabolic rate” means the speed at which your body burns energy. Put together, it is the minimum number of calories your body needs in 24 hours to keep its essential systems running while you do nothing at all. Breathing, circulating blood, repairing cells, filtering blood through the kidneys and liver, keeping your brain and nerves firing, and holding your core temperature at about 98.6°F all cost energy, and that cost is your BMR.

In a lab, BMR is measured first thing in the morning, after a night’s sleep and 12 hours without food, lying still in a quiet, temperature-controlled room. Almost nobody is measured that way. In practice, “BMR” nearly always means a number from a formula, which is close enough for everyday use. The Cleveland Clinic gives typical averages of about 1,700 calories a day for men and 1,400 for women, with the caveat that individuals vary widely.

Where do those calories go? Roughly a fifth each to the liver and the brain, about a fifth to resting muscle, a tenth to the heart and a tenth to the kidneys, and the rest spread across everything else. Muscle is the one you can change, which matters later.

How to calculate your BMR

The formula that doctors and dietitians use most is Mifflin-St Jeor, published in 1990 after measurements on nearly 500 adults. When the Academy of Nutrition and Dietetics compared the common formulas against lab measurements in 2005, Mifflin-St Jeor came out as the most reliable, landing within 10 percent of the true figure for most people. Here it is, with the US unit conversions built in.

1. Convert your weight to kilograms: pounds divided by 2.2.
2. Convert your height to centimeters: total inches multiplied by 2.54.
3. Multiply weight in kg by 10.
4. Add height in cm multiplied by 6.25.
5. Subtract your age multiplied by 5.
6. Add 5 if you are a man. Subtract 161 if you are a woman.

Worked example, woman

35 years old, 5 feet 7 inches, 150 pounds. Weight is 150 divided by 2.2, which is 68.2 kg. Height is 67 inches times 2.54, which is 170.2 cm. So: 10 times 68.2 is 682. Plus 6.25 times 170.2 is 1,064, giving 1,746. Minus 5 times 35 is 175, giving 1,571. Minus 161 for a woman gives a BMR of about 1,410 calories a day.

Worked example, man

35 years old, 6 feet, 200 pounds. Weight is 90.9 kg. Height is 72 inches times 2.54, which is 182.9 cm. So: 909, plus 1,143, giving 2,052. Minus 175 for age gives 1,877. Plus 5 for a man gives a BMR of about 1,880 calories a day.

If you would rather not do the arithmetic, our TDEE calculator shows your BMR alongside your maintenance calories and goal targets, and it switches to a lean-mass formula if you know your body fat percentage.

The other formulas

• Harris-Benedict, from 1919 and revised in 1984. The original formula and the one most older calculators still use. It tends to overestimate BMR by about 5 percent compared with Mifflin-St Jeor, which is why Mifflin replaced it.
• Katch-McArdle works from lean body mass, so it needs your body fat percentage. If you know that number from a reliable measurement, it is the better choice for very muscular or very lean people, because it does not assume an average body composition.
• Cunningham is a similar lean-mass formula used mostly with athletes.

For most people the differences between them are 50 to 100 calories, well inside the margin of error. Pick one and stop worrying about it.

How BMR is measured in a lab

Every formula is an estimate. The real measurement is called indirect calorimetry. You lie still under a clear hood or wear a mask for 10 to 30 minutes, usually after an overnight fast, while a machine measures the oxygen you breathe in and the carbon dioxide you breathe out. Those numbers convert directly into calories. A true BMR test means waking up in the lab after a night’s sleep, so most clinics, dietitians, and some gyms offer the simpler resting metabolic rate (RMR) test instead, which comes very close. It is worth considering if formulas keep giving numbers that do not match your results, for example if you are very muscular, have a lot of weight to lose, or have a thyroid condition.

What is a normal BMR? Average by age and sex

People ask whether their number is good, bad, or normal, and the honest answer is that BMR is mostly a reflection of your size, so there is no good or bad, only expected. The table below gives the Mifflin-St Jeor BMR for an adult of average US height and weight, which the CDC puts at about 5 feet 9 inches and 199 pounds for men and 5 feet 4 inches and 171 pounds for women. Your own number will be higher if you are bigger or more muscular and lower if you are smaller.

Two things stand out. First, BMR drops about 50 calories per decade in the formula, and in real life a little more, because most people also lose muscle as they age. Second, the gap between men and women is mostly a size and muscle gap, not a mystery of biology. A woman and a man of identical height, weight, and body composition have nearly identical BMRs.

So is a BMR of 1,400 good? Is 1,500?

For an average-sized woman between 35 and 50, 1,400 to 1,500 is exactly what the formula predicts, so it is normal. For a 6-foot man it would be low and worth a second look at the inputs. The number itself is not a score. What matters is what you do with it, which is the next section.

BMR vs RMR vs TDEE vs maintenance calories

These four terms get used as if they were interchangeable, and they are not. The confusion causes real mistakes, usually people eating far too little.

Most online “BMR calculators” actually report RMR, and most people use the two words to mean the same thing. That is fine. The distinction that matters is between BMR and TDEE, because TDEE is the number you eat around, not BMR. Our guide to maintenance calories and how to find yours covers that side in detail.

Should I eat my BMR to lose weight?

No, and this is the single most common mistake people make with the number. Your BMR is what you burn lying still. You do not lie still all day. Once you add walking, working, cooking, and digesting food, you burn 20 to 90 percent more than your BMR. Eating only your BMR therefore puts you in a much larger deficit than you think, often 700 to 1,000 calories a day, which leads to hunger, fatigue, muscle loss, and the kind of diet nobody can keep up.

The right approach is to turn BMR into TDEE first. Multiply by 1.2 if you are sedentary, 1.375 if lightly active, 1.55 if moderately active, 1.725 if very active, and 1.9 if you train hard every day or have a physical job. Then eat 250 to 500 calories below that TDEE to lose weight at a sustainable half a pound to a pound a week. Many dietitians use BMR as a floor: it is reasonable not to eat below it for any length of time without medical supervision.

Example: how many calories should I eat if my BMR is 1,500?

If your BMR is 1,500 and you have a desk job with a couple of workouts a week, you are lightly active and your TDEE is about 1,500 times 1.375, which is roughly 2,060. To lose a pound a week, eat around 1,560. To lose half a pound a week, around 1,810. Both keep you at or above your BMR. If you are moderately active, your TDEE is about 2,325 and the targets move up by about 260 calories. For the full ranges by age and goal, see our guide to how many calories you should eat a day.

What changes your BMR

• Body size. The biggest factor. More body, more cells to keep alive. This is why BMR falls as you lose weight, by roughly 4 to 5 calories a day for each pound lost. Your total daily burn falls more, about 10 to 15 calories per pound, because moving a lighter body takes less energy too.
• Muscle mass. Muscle burns more at rest than fat, about 6 calories per pound per day against roughly 2 for fat. Not the 50 calories per pound that gym folklore claims, but over 20 or 30 pounds of muscle it adds up.
• Age. Roughly 2 to 3 percent per decade after your twenties, mostly through lost muscle.
• Sex. Men average higher because they average larger and more muscular. Matched for size and composition, the difference nearly disappears.
• Genetics. Real but smaller than people assume, usually within about 10 percent of what size and composition predict.
• Thyroid. An underactive thyroid lowers BMR, often by 5 to 15 percent in untreated cases, and an overactive one raises it. Treatment brings it back toward normal.
• Menopause and medicines. BMR tends to dip around menopause, mostly through muscle loss. Some medicines, including beta-blockers, certain antidepressants, and antipsychotics, are linked with weight gain, partly through appetite and partly through a small drop in energy use. Do not stop a medicine on your own; ask your doctor about alternatives.
• Crash dieting. A long, steep deficit lowers BMR a little beyond what the weight loss alone explains, usually 5 to 10 percent. It recovers when you eat at maintenance again.
• Temperature, illness, and pregnancy all raise it temporarily. Fever in particular can raise it by around 7 percent per degree Fahrenheit.

Can you raise your BMR?

Honestly, a little, and only one way works reliably. Building muscle through strength training two or three times a week raises BMR by a modest but permanent amount and, more importantly, stops the slow loss of muscle that drags BMR down with age. Eating enough protein, around 0.7 grams per pound of body weight, protects that muscle, and protein also costs more to digest than fat or carbohydrate. Beyond that, the popular claims fall apart. Green tea, spicy food, cold showers, and “metabolism-boosting” supplements change BMR by a few calories at most, for a few hours. Eating small frequent meals does not raise it. Drinking cold water does not raise it meaningfully. Sleep, on the other hand, matters more than people think: short sleep lowers the energy you burn at rest and raises hunger, so it hits both sides of the equation.

The honest framing is that the lever worth pulling is not BMR but the rest of TDEE. Your daily movement, the walking and standing and general activity outside the gym, can vary by several hundred calories a day between people of the same size, and it is entirely in your control.

BMR and hypothyroidism

An underactive thyroid slows metabolism, which is why weight gain and feeling cold are classic symptoms. In untreated hypothyroidism, BMR can run 5 to 15 percent below what the formula predicts, so a woman the formula puts at 1,400 might truly sit nearer 1,250. Once thyroid hormone is replaced and levels are normal, BMR returns close to the predicted range, and the formula becomes reliable again. If you have hypothyroidism and the calculator numbers never seem to match your experience, that is the reason, and it is worth asking your doctor whether your dose is right rather than cutting calories further.

When to talk to a doctor

See a doctor if you are gaining or losing weight in a way your calorie numbers cannot explain, if you feel constantly cold, tired, or sluggish, if your hair is thinning or your periods have changed, or if you cannot lose weight on a sensible deficit after two months of honest tracking. A thyroid blood test is simple and rules the most common metabolic cause in or out. Also get advice before using any of these numbers if you are pregnant, breastfeeding, under 18, or have a history of disordered eating.

The bottom line

BMR is the calories your body burns at rest, roughly 1,400 for an average woman and 1,700 for an average man, and the Mifflin-St Jeor formula gives yours in two minutes. It is a floor and a building block, not a target. Multiply it by your activity level to get your maintenance calories, eat a little below that to lose weight, and do not eat below your BMR for long. Build and keep muscle if you want the number to stay high as you age, and ignore anything that promises to boost it with a drink or a pill.

Frequently asked questions