BMR Calculator

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Weight

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Age

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Formula

* Uses body fat percentage

What Is Basal Metabolic Rate?

You use energy no matter what you're doing, even when sleeping. The BMR Calculator will calculate your Basal Metabolic Rate (BMR); the number of calories you'd burn if you stayed in bed all day and did nothing else. It accounts for about 60 to 75% of all calories you burn in a typical day. The rest comes from physical activities and digesting food.

If you've noticed that every year, it becomes harder to eat whatever you want and stay slim, you've also learnt that your BMR decreases as you age. Likewise, depriving yourself of food in hopes of losing weight also decreases your BMR, a foil to your intentions.

However, a regular routine of cardiovascular exercise can increase your BMR, improving your health and fitness when your body's ability to burn energy gradually slows down.

Once you know your BMR, you can calculate your daily calorie needs based on your activity level using the Harris Benedict formula.

What Affects Your BMR?

Your BMR isn't set in stone, it fluctuates based on several factors:

Muscle mass Muscle burns more calories than fat does, even at rest. 2 people weighing the same can have very different BMRs if one of them is more muscular.

Body size Bigger bodies need more energy to function, plain and simple. A 200-pound person will always have a higher BMR than a 130-pound person.

Age Starting in your 30s, muscle mass starts to gradually decline unless you actively work to maintain it. This is what is lowering your BMR over time.

Sex Men typically have a higher BMR than women because they carry more muscle and less fat.

Genetics According to a 2005 study, there's a 25% variance in BMR between people that can't be explained by any of the usual factors.

Hormones Hormonal changes can affect your BMR. An underactive thyroid slows everything down while an overactive one speeds things up. Pregnancy and breastfeeding also have an impact.

Dieting Going on extreme diets can lower your BMR. When you cut calories too drastically, your body will adapt by burning fewer calories. This is why some crash diets end up backfiring.

Temperature Your body works harder (and burns extra calories) when it's trying to keep you warm or cool you down.

What's the difference between BMR and TDEE?

BMR tells you how many calories you're burning at rest. TDEE (total daily energy expenditure), however, is what you actually burn over an entire day: including both your BMR and additional calories burned through physical activity and digestion.

To estimate your TDEE, just take your BMR and multiply it by an activity factor:

Activity Level	Description	Multiply BMR by
Sedentary	Desk job, little or no exercise	1.2
Light	Light exercise 1-3 days per week	1.375
Moderate	Moderate exercise 3-5 days per week	1.55
Active	Hard exercise 6-7 days per week	1.725
Extra	Very hard exercise + physical job	1.9

For instance, if your BMR is around 1,600 calories and you're moderately active, your TDEE would be 2,480 calories per day (1,600 x 1.55). That's how many calories you'd need to eat to maintain your current weight.

For a more accurate estimate, consider trying our TDEE calculator.

Are BMR and RMR the same thing?

Sometimes people use the terms BMR and RMR (Resting Metabolic Rate) interchangeably, but there's a (slight) difference.

BMR is measured under strict lab conditions: A full night's sleep in a temperature-controlled room while lying perfectly still, after fasting for about 12 hours.

RMR is measured in a much more relaxed setting (imagine hanging out at home all day in bed). Because of this, RMR readings tend to be around 10% higher than BMR readings.

Still, the difference is usually minor enough that it doesn't really matter. Most online calculators estimate BMR using formulas that are close enough for practical use.

What's Considered a Normal BMR?

A person's BMR can range anywhere between 1,000 to over 2,500 calories per day. Naturally, a small, older woman will have a lower BMR compared to a young muscular man. It simply reflects the amount of energy a particular body needs.

In general adult males have a BMR of about 1,600 to 1,700 calories per day while adult females have a BMR of about 1,400 to 1,500 calories per day.

How to Use Your BMR Results

Your BMR can help you guide how many calories you should eat in a day:

To maintain your weight: Multiply your BMR by your activity level from the table earlier to get your TDEE. Eat around that many calories per day to maintain your weight.

To lose weight: Try eating below your TDEE, not below your BMR. A deficit of about 500 calories per day works out to losing roughly one pound per week without risking muscle loss or slowing down your metabolism.

To gain weight: Add an extra 300 to 500 calories above your TDEE each day for gradual weight gain. Pair this with strength training so that the extra weight is muscle instead of fat.

Keep in mind that as your weight changes, so does your BMR. If you lose 20 pounds, your body needs fewer calories to maintain itself. Recalculate your BMR to keep your targets accurate.

For more detailed guidance see our page on daily calorie needs using the Harris-Benedict equation.

Which BMR Formula Should You Use?

This calculator lets you pick from 7 different formulas for calculating your BMR! Here's who they work best for:

Best for most people

Mifflin-St Jeor

According to a 2005 study by the American Dietetic Association this formula is considered the most accurate. It factors in age, sex, weight and height.

Best if you know your body fat %

Katch-McArdle

This formula uses lean body mass instead of just weight, height and age making it much more accurate for very lean or muscular people.

Best for athletes

Cunningham

Similar to Katch-McArdle but often preferred by athletes due to its slightly higher estimates using lean body mass.

Most diverse research

Oxford

Built from over 10,000 BMR measurements across a diverse range of subjects. We label it "most reliable" on this site for this reason.

Classic formula

Harris-Benedict

Being one of the oldest formulas around (dating back to 1918 and revised in 1984), it slightly overestimates compared to newer formulas but remains widely used.

Used by WHO

Schofield

This formula is used by the World Health Organization but keep in mind that its data comes mostly from Italian male subjects which might skew the results for other populations.

If you're unsure which one fits best for you, select "All Formulas" in our calculator so you can see results side-by-side!

How to Increase Your BMR

There are some things that you can influence that have an effect on your BMR:

Build muscle. Muscle burns more calories than fat, even when you're resting. Regular strength training helps add lean mass which keeps your metabolism higher throughout the day.

Eat enough protein. Your body works harder digesting protein. It's also key for building and maintaining muscle. Aim for about one gram of protein per pound of body weight if you're active!

Stay active throughout the day. Simple stuff like walking more helps elevate your overall calorie burn and lead to a higher resting metabolism.

Get enough sleep. Not sleeping at least 8 hours per night could drop your resting metabolic rate by about 2.6%. Lack of sleep also messes with hormones that regulate hunger and fat storage.

Whatever you do, don't starve yourself! This approach makes the body conserve energy resulting in a lower metabolic rate, which is counterproductive.

Frequently Asked Questions

Should I eat at my BMR if I'm trying to lose weight?

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No, your BMR represents the bare minimum your body needs to function (without considering any movement). Eating right at this number would create a large calorie deficit which can slow down your metabolism and cause muscle loss. Instead, calculate your TDEE and eat 500 calories below that number.

Is having a high BMR good or bad?

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Neither really, a high BMR simply means your body simply burns more calories at rest. It is not necessarily indicative of better health by itself.

Why does my BMR vary between different calculators?

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Different calculators rely on varying formulas which produce slightly different results, usually within the 100 to 200 calorie range. Our calculator lets you use the 7 most used BMR formulas.

Can you actually change your BMR?

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To some extent, yes. Building muscle is the best way to raise your BMR, but crash dieting will lower it. Don't expect dramatic changes though, it's limited overall.

Does BMR decline with age?

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Studies show metabolism stays relatively stable until age 60. After that, it starts to decline by about 0.7% per year. But don't sweat it too much, if you maintain your muscles you can slow the decline significantly!

How accurate are BMR calculators?

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Each formula is an estimate based on population averages, but in general they are accurate within a 10% margin. The margin is due to individual variances such as body composition, hormones, etc.

BMR Formulas Used:

Note that all formulas are in metric notation.

Harris Benedict Formula (Original):

The original Harris Benedict formula is one of the most used formulas on the internet to calculate your daily energy needs, however it is also one of the least accurate.

Males: 66.4730 + (13.7516 x Weight [kg]) + (5.0033 x Height [cm]) - (6.7550 x Age)
Females: 655.0955 + (9.5634 x Weight [kg]) + (1.8496 x Height [cm]) - (4.6756 x Age)

Harris Benedict Formula (Revised):

In 1984, the Harris Benedict formula was revised by Roza and Shizgal. A larger research group was used.

Males: 88.362 + (13.397 x Weight [kg]) + (4.799 x Height [cm]) - (5.677 x Age)
Females: 447.593 + (9.247 x Weight [kg]) + (3.098 x Height [cm]) - (4.33 x Age)

Mifflin-St Jeor:

In 1990 the Mifflin-St Jeor formula was introduced. In 2005 The American Dietetic Association (ADA) compared the BMR formulas of Harris-Benedict, Mifflin-St Jeor, Owen and WHO/FAO/UNU and found that Mifflin-St Jeor was the most accurate, predicting RMR within 10% of measured values.

Males: (9.99 x Weight [kg]) + (6.25 x Height [cm]) - (4.92 x Age) + 5
Females: (9.99 x Weight [kg]) + (6.25 x Height [cm]) - (4.92 x Age) - 161

Schofield:

The Schofield equation was published in 1985 and used by FAO/WHO/UNU (World Health Organization and others). However, a disproportionate number of subjects in the data set were Italian men with on average higher BMR values. This skewed the results for other communities.

Males:

0–359.512 × Weight (kg) − 30.4

3–1022.706 × Weight (kg) + 504.3

10–1817.686 × Weight (kg) + 658.2

18–3015.057 × Weight (kg) + 692.2

30–6011.472 × Weight (kg) + 873.1

60+11.711 × Weight (kg) + 587.7

Females:

0–358.317 × Weight (kg) − 31.1

3–1020.315 × Weight (kg) + 485.9

10–1813.384 × Weight (kg) + 692.6

18–3014.818 × Weight (kg) + 486.6

30–608.126 × Weight (kg) + 845.6

60+9.082 × Weight (kg) + 658.5

Oxford (Most Reliable):

As the Schofield equation above was proven not to be very reliable for many, a new series of equations was developed in 2005 which consisted of a database of 10,552 BMR values that had a more diverse set of subjects.

Males:

0–361.0 × Weight (kg) − 33.7

3–1023.3 × Weight (kg) + 514

10–1818.4 × Weight (kg) + 581

18–3016.0 × Weight (kg) + 545

30–6014.2 × Weight (kg) + 593

60+13.5 × Weight (kg) + 514

Females:

0–358.9 × Weight (kg) − 23.1

3–1020.1 × Weight (kg) + 507

10–1811.1 × Weight (kg) + 761

18–3013.1 × Weight (kg) + 558

30–609.74 × Weight (kg) + 694

60+10.1 × Weight (kg) + 569

Katch-McArdle:

Both the Katch-McArdle and the Cunningham formulas use lean body mass to estimate your resting metabolic rate. If you know your body fat percentage, lean body mass can be calculated by the following formula: (1 - Body Fat Percentage / 100) x Weight. Note that in the BMR/RMR calculator above the lean body mass is automatically calculated using the Boer formula if body fat percentage is not provided.

370 + (21.6 x Lean Body Mass [kg]))

Cunningham:

The Cunningham equation is more accurate for very athletic people.

500 + (22 x Lean Body Mass [kg]))

Note: 1 kilogram (kg) = 2.2 pounds (lb), 1 meter = 3.28084 feet

References

Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241-247.
Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. J Am Diet Assoc. 2005;105(5):775-789.
Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021;373(6556):808-812.
Harris JA, Benedict FG. A biometric study of human basal metabolism. Proc Natl Acad Sci USA. 1918;4(12):370-373.
Henry CJK. Basal metabolic rate studies in humans: measurement and development of new equations. Public Health Nutr. 2005;8(7A):1133-1152.
Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168-182.