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Free BMR Calculator

The basal metabolic rate (BMR) calculator finds out how many calories your body burns at rest, specifically when your digestive system is inactive, after about 12 hours of fasting. Factors like your muscle mass, age, diet, genetics, and total daily energy expenditure (TDEE) can also affect your BMR.

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Understanding BMR

What Is BMR?

Basal Metabolic Rate, or BMR, is the amount of energy your body uses to support basic life-sustaining functions while at complete rest, commonly known as "metabolism".

Think of it as your body’s baseline energy use, or calories burnt a day, before movement, exercise, or digestion are added. For many adults, BMR makes up the largest share of total daily calories burnt, while physical activity and digestion account for the rest.

How BMR Is Calculated

BMR can be estimated using 3 widely recognised equations based on factors such as weight, height, age, sex, and sometimes body fat percentage. Our BMR calculator lets you choose from three formulas:

  1. Mifflin-St Jeor: Often used as a standard equation for the general adult population.
    • Men: BMR = 10W + 6.25H - 5A + 5
    • Women: BMR = 10W + 6.25H - 5A - 161
  2. Revised Harris-Benedict: An updated version of the classic Harris-Benedict equation.
    • Men: BMR = 13.397W + 4.799H - 5.677A + 88.362
    • Women: BMR = 9.247W + 3.098H - 4.330A + 447.593
  3. Katch-McArdle: Often used when lean body mass or body fat percentage is available.
    • Formula: BMR = 370 + 21.6 × (1 - F) × W

Where W = weight in kg, H = height in cm, A = age, and F = body fat as a decimal, such as 0.20 for 20% body fat.

How to Use BMR to Estimate TDEE

Your BMR is your baseline calorie burnt when your body is at complete rest. To estimate your Total Daily Energy Expenditure, or TDEE, multiply your BMR by an activity factor:

  • Sedentary — Little or no exercise: BMR × 1.2
  • Lightly Active — Exercise 1–3 times per week: BMR × 1.375
  • Moderately Active — Exercise 4–5 times per week: BMR × 1.465
  • Active — Intense exercise 3–4 times per week, or daily exercise: BMR × 1.55
  • Very Active — Intense exercise 6–7 times per week: BMR × 1.725
  • Extra Active — Very intense daily exercise, or a physically demanding job: BMR × 1.9

What BMR Can Tell You

Your BMR is the foundation of your diet. When combined with TDEE, it can help you set daily calorie targets for weight loss, weight maintenance, or muscle gain.

What Can Affect Your BMR?

Your BMR can be influenced by age, sex, height, weight, muscle mass, body composition, hormones, genetics, and overall health.

In general, people with more lean muscle mass tend to have a higher BMR because muscle tissue requires more energy to maintain than fat tissue.

This is why two people with the same weight can have different daily calorie needs.

FAQ

Unlike BMI, there is no single "normal" or healthy range for BMR. Your BMR is entirely unique to your body size, composition, age, and gender. A larger, more muscular person will naturally have a higher BMR than a smaller person.

No. Eating below your BMR is generally not recommended, as your body needs those calories just to keep your organs functioning properly. To lose weight safely, you should calculate your TDEE (BMR multiplied by your activity level) and eat slightly fewer calories than your TDEE, rather than eating below your BMR.

BMR (Basal Metabolic Rate) and RMR (Resting Metabolic Rate) are often used interchangeably, but there is a slight difference. BMR measures your absolute minimum energy needs under strict resting conditions (usually after fasting and a full night's sleep). RMR measures calories burned at rest but under less strict conditions. RMR is usually slightly higher than BMR.

Your BMR, or basal metabolic rate, may increase by increasing your lean muscle mass, being physically active and consuming enough calories. Strength training, like squat, bench, and deadlift (SBD), can increase your muscle tissue, which ultimately uses more energy to sustain than fat training, thus increasing your BMR.

Your metabolic rate is not fixed. It is a highly dynamic number influenced by a variety of biological, environmental, and lifestyle variables:
  • Muscle Mass: While cardiovascular workouts (like cycling) burn calories in the moment, they don't significantly alter your baseline metabolism. Strength training builds muscle tissue, which requires far more energy to maintain than fat. The higher your muscle-to-fat ratio, the more calories your body burns at rest.
  • Age: As we grow older, our metabolic engines metabolism naturally begin to slow down. Older adults generally require fewer baseline calories to support vital organ functions compared to when they were younger.
  • Genetics: Your DNA plays a foundational role. The traits inherited from your family can directly dictate whether you naturally possess a faster or slower metabolic rate.
  • Weather and Temperature: Extreme environments force your body to work harder. In freezing weather, your body burns extra energy to maintain its core temperature. Conversely, extreme heat also raises your BMR as your body expends energy to cool itself down. There is a 7% increase in BMR for every 1.36 degrees Fahrenheit in the body's core.
  • Dietary Habits: Regular eating habits help maintain an active metabolism. However, severe calorie restriction can crash your BMR by up to 30%. A starving body will deliberately slow down bodily functions and energy levels to conserve its remaining fuel.
  • Pregnancy and Hormones: Growing a baby requires a tremendous amount of internal energy, naturally driving up a pregnant woman's baseline caloric needs. Furthermore, major hormonal shifts, such as those occurring during menopause, can cause your metabolic rate to fluctuate.
  • Supplements: Certain dietary substances, such as caffeine, act as stimulants that can temporarily boost your central nervous system and raise your BMR.

No. A TDEE calculator measures the total calories you burn in an entire day, whereas a BMR calculator calculates the calories you burn at rest. In other words, the TDEE calculator has a more comprehensive overview for your entire day, but the BMR calculator essentially measures a sliver of your entire day.
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