BMR Calculator

Estimate your Basal Metabolic Rate, the calories your body burns at rest, plus daily calorie needs for every activity level.

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Tell us about you so we can estimate your BMR.

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BMR estimates are educational and depend on the formula and inputs used. They are not a substitute for clinical assessment.

What BMR actually measures

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest, just to stay alive. That covers breathing, pumping blood, repairing cells, and keeping your organs running. Think of it as the energy you'd spend lying in bed all day, without moving a muscle on purpose.

BMR is the baseline that almost every calorie plan builds on. Once you know it, the rest of your daily energy needs start to make sense.

Why does your BMR matter?

Your BMR tells you the minimum fuel your body needs each day. Most of the calories you burn aren't from exercise. They go toward simply keeping you running in the background.

For most people, BMR makes up 60 to 70 percent of the calories they burn daily. So if you want to lose, gain, or hold your weight, this number is where the math begins.

How is BMR calculated?

Most calculators use the Mifflin-St Jeor equation, which doctors and dietitians widely trust. It takes four things about you and estimates your resting calorie burn from them.

You'll usually be asked for your:

  • Age
  • Sex assigned at birth
  • Height
  • Weight

The result is an estimate, not a lab reading. Still, it's accurate enough for everyday planning around food and activity.

What affects your BMR?

Several things shape how fast your body burns calories at rest. Some you can change, and some you can't. Knowing them helps you read your number with the right context.

Here are the main factors, from the ones that matter most to the smaller ones:

  • Muscle mass. Muscle burns more calories at rest than fat, so more muscle means a higher BMR.
  • Body size. A larger body needs more energy to run, so taller and heavier people tend to have a higher BMR.
  • Age. BMR usually drops with age as muscle naturally declines.
  • Sex. Men often have a higher BMR than women because they tend to carry more muscle.
  • Genetics. Some people simply run a little faster or slower than average.
  • Hormones. Thyroid problems and other hormone shifts can raise or lower your BMR.

So if your number looks different from a friend's, that's normal. Two people of the same weight can have very different resting needs.

What's the difference between BMR and TDEE?

Your BMR is what you burn at rest. Your TDEE, or Total Daily Energy Expenditure, adds everything else on top.

TDEE includes the calories you burn from walking, working out, and even digesting food. It's always the bigger number, and it's the one you actually plan your meals around. To find yours, you can use the TDEE Calculator once you know your BMR.

How do you use your BMR for weight goals?

Your BMR is the starting point, not the eating target. You build your daily calorie goal around your TDEE, then adjust up or down depending on what you want.

Here's the simple version of how it works:

  1. Find your BMR with this calculator.
  2. Estimate your TDEE by adding your daily activity.
  3. To lose weight, eat slightly below your TDEE.
  4. To gain weight, eat slightly above it.
  5. To stay the same, eat around your TDEE.

Small, steady changes work better than drastic ones. A modest deficit is easier to stick with and gentler on your body.

Should you ever eat below your BMR?

It's usually not a good idea. Eating below your BMR for long stretches can leave you tired, hungry, and low on nutrients.

Your body needs those baseline calories to function well. Most healthy plans set your target below your TDEE instead, which still creates a deficit without dropping under your resting needs. If you're thinking about a very low calorie diet, talk to a doctor or dietitian first.

Why does BMR change over time?

Your BMR isn't fixed. It shifts as your body and habits change, which is why it helps to recalculate now and then.

A few common reasons your number moves:

  • Weight loss. A smaller body needs fewer calories, so BMR falls as you lose weight.
  • Aging. Muscle slowly declines with age, which lowers BMR.
  • Strength training. Building muscle can nudge your BMR back up.
  • Health changes. Thyroid and hormone shifts can raise or lower it.

This is one reason weight loss often slows over time. Recalculating every few weeks keeps your plan realistic.

What if your BMR seems too high or too low?

A single surprising number is rarely a cause for worry. These calculators give estimates, and normal ranges are wide.

That said, if you feel constantly exhausted, gain or lose weight without trying, or notice changes in your temperature, heart rate, or mood, it's worth checking in with a doctor. Sometimes a very high or low metabolism points to a thyroid issue or another condition worth looking into.

Putting your number to use

Once you have your BMR, you've got the foundation for almost any nutrition plan. Pair it with your activity level for your TDEE, and you'll know roughly how much to eat for your goal.

If you want to go further, the DRI Calculator can break down your specific macros and nutrients, and the Hydration Calculator helps you sort out your daily fluids. Your BMR is just the first piece, and a helpful one to start with.

Questions about metabolism, calories, or weight?

august is a private AI health companion that can help explain your BMR, what it means for your goals, and how to use the number wisely.

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Frequently Asked Questions

There's no single normal number. BMR depends on your age, sex, height, weight, and muscle mass. As a rough guide, many adult women sit between 1,200 and 1,500 calories a day, and many adult men between 1,600 and 1,900. Yours can fall outside that and still be healthy.

Most calculators use the Mifflin-St Jeor equation. It takes your weight, height, age, and sex to estimate resting calorie burn. It's an estimate, not a lab measurement, but it's accurate enough for everyday planning.

BMR is what you burn at rest. TDEE (Total Daily Energy Expenditure) adds your daily movement, exercise, and digestion on top. TDEE is the bigger number, and it's what you actually eat around. You can check yours with our TDEE Calculator.

It's usually not a good idea. Eating below your BMR for long can leave you tired, hungry, and short on nutrients. Most plans set your calorie target below your TDEE instead, which still creates a deficit without dropping under your resting needs.

You tend to lose muscle with age, and muscle burns more calories at rest than fat does. So the same person often has a lower BMR at 50 than at 25. Strength training can slow that decline.

Yes. A smaller body needs fewer calories to run, so your BMR falls as you lose weight. That's one reason weight loss can slow over time, and why recalculating every few weeks helps.