Free BMR Calculator

Free BMR Calculator

Calculate Your Basal Metabolic Rate

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest—just to keep you alive (breathing, circulation, cell production). Use this calculator to find your BMR and see how many calories you need based on your activity level.
ft
in
Your Basal Metabolic Rate
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Calories/day
Daily Calorie Needs Based on Activity Level
Activity Level Calories
Sedentary (little or no exercise) -
Lightly Active (exercise 1-3 times/week) -
Moderately Active (exercise 4-5 times/week) -
Active (daily exercise or intense 3-4 times/week) -
Very Active (intense exercise 6-7 times/week) -
Extremely Active (very intense daily exercise or physical job) -
Exercise: 15-30 minutes of elevated heart rate activity.
Intense exercise: 45-120 minutes of elevated heart rate activity.
Very intense exercise: 2+ hours of elevated heart rate activity.
Note: BMR is calculated using the Mifflin-St Jeor equation, which is considered the most accurate formula for estimating basal metabolic rate. Your actual calorie needs may vary based on factors like muscle mass, genetics, and overall health.

What is Basal Metabolic Rate (BMR)?

Basal Metabolic Rate (BMR) is the number of calories your body needs to perform its most basic (basal) life-sustaining functions. These include breathing, circulation, cell production, nutrient processing, protein synthesis, and ion transport. In simpler terms, BMR is the amount of energy your body burns while completely at rest.

BMR accounts for approximately 60-75% of your total daily energy expenditure. The remaining calories are burned through physical activity and the thermic effect of food (energy used to digest what you eat).

BMR vs. RMR: What's the Difference?

You may also hear about Resting Metabolic Rate (RMR). While often used interchangeably, there's a subtle difference:

BMR (Basal Metabolic Rate)

Measured under very strict conditions: after 8 hours of sleep, 12 hours of fasting, in a temperature-controlled room, with no physical activity or emotional stress.

RMR (Resting Metabolic Rate)

Measured under less restrictive conditions. Typically 10-20% higher than BMR because conditions aren't as controlled.

For practical purposes, most calculators (including this one) estimate RMR but call it BMR. The difference is minimal and doesn't significantly affect calorie planning.

How is BMR Calculated?

Several formulas exist to estimate BMR. This calculator uses the Mifflin-St Jeor equation, which research has shown to be the most accurate for most people.

Mifflin-St Jeor Equation (1990)

For Men:
BMR = (10 Ă— weight in kg) + (6.25 Ă— height in cm) - (5 Ă— age) + 5
For Women:
BMR = (10 Ă— weight in kg) + (6.25 Ă— height in cm) - (5 Ă— age) - 161

Example Calculation

For a 30-year-old male who weighs 180 lbs (81.6 kg) and is 5'10" (177.8 cm):

BMR = (10 Ă— 81.6) + (6.25 Ă— 177.8) - (5 Ă— 30) + 5
BMR = 816 + 1111.25 - 150 + 5
BMR = 1,782 calories/day

Other BMR Formulas

Formula Year Notes
Harris-Benedict 1918 Original formula, tends to overestimate by ~5%
Revised Harris-Benedict 1984 Updated version, more accurate than original
Mifflin-St Jeor 1990 Most accurate for most populations (used here)
Katch-McArdle 1996 Uses lean body mass; best for lean/athletic individuals

Understanding TDEE (Total Daily Energy Expenditure)

Your BMR only tells part of the story. To know how many calories you actually burn each day, you need to calculate your Total Daily Energy Expenditure (TDEE), which includes:

60-75%
BMR
Calories burned at complete rest
15-30%
Physical Activity
Exercise and daily movement
10%
TEF
Thermic Effect of Food (digestion)

TDEE is calculated by multiplying your BMR by an activity factor:

Activity Level Multiplier Description
Sedentary 1.2 Little or no exercise, desk job
Lightly Active 1.375 Light exercise 1-3 days/week
Moderately Active 1.55 Moderate exercise 3-5 days/week
Very Active 1.725 Hard exercise 6-7 days/week
Extremely Active 1.9 Very hard exercise, physical job, training 2x/day

Factors That Affect BMR

Your BMR isn't fixed—it can change based on many factors:

Factors that INCREASE BMR
  • More muscle mass
  • Larger body size
  • Younger age
  • Being male (generally)
  • Higher body temperature/fever
  • Stimulants (caffeine, nicotine)
  • Cold environments
  • Pregnancy/lactation
  • Growth periods
Factors that DECREASE BMR
  • Less muscle mass
  • Smaller body size
  • Older age
  • Being female (generally)
  • Prolonged calorie restriction
  • Lack of sleep
  • Hormonal imbalances
  • Crash dieting
  • Loss of lean tissue

Why Muscle Mass Matters

One of the most important factors affecting BMR is your muscle mass. Muscle tissue is metabolically active—it burns calories even at rest. In contrast, fat tissue is relatively inactive metabolically.

The Numbers:
  • 1 pound of muscle burns approximately 6-7 calories per day at rest
  • 1 pound of fat burns approximately 2-3 calories per day at rest

While this difference may seem small, it adds up. Someone with 20 extra pounds of muscle burns roughly 80-100 more calories per day than someone with 20 extra pounds of fat—even while doing nothing!

How to Increase Your BMR

  • Build muscle through resistance training — Weight lifting, bodyweight exercises, and resistance bands all help build metabolically active tissue.
  • Don't crash diet — Severe calorie restriction causes your body to lower its metabolic rate to conserve energy. Aim for moderate deficits (15-25%).
  • Eat enough protein — Protein has a higher thermic effect (20-30%) compared to carbs (5-10%) or fats (0-3%), meaning you burn more calories digesting it.
  • Stay active throughout the day — NEAT (Non-Exercise Activity Thermogenesis) like walking, fidgeting, and standing can significantly boost total calorie burn.
  • Get quality sleep — Poor sleep disrupts hormones that regulate metabolism, including cortisol, leptin, and ghrelin.
  • Stay hydrated — Studies show that drinking cold water can temporarily boost metabolism by 24-30% for about an hour.
  • Don't skip meals — Eating regularly helps maintain stable blood sugar and metabolic function.

Using BMR for Weight Management

For Weight Loss

To lose weight, you need to consume fewer calories than your TDEE. A safe and sustainable deficit is typically:

  • Mild deficit (10-15%): Slow, sustainable weight loss (~0.5 lb/week)
  • Moderate deficit (20-25%): Standard weight loss (~1 lb/week)
  • Aggressive deficit (25-30%): Faster loss but harder to maintain (~1.5 lb/week)

Important: Never eat below your BMR for extended periods. This can slow your metabolism, cause muscle loss, and lead to nutrient deficiencies.

For Weight Gain

To gain weight (ideally muscle), eat above your TDEE:

  • Lean bulk: 10-15% surplus (minimize fat gain)
  • Standard bulk: 15-20% surplus (balanced approach)
  • Aggressive bulk: 20%+ surplus (faster gains, more fat)

For Maintenance

To maintain your current weight, eat at your TDEE. Track your weight for 2-3 weeks and adjust if needed—calculators provide estimates, not exact numbers.

Common Misconceptions About BMR

❌ Myth: "I have a slow metabolism"

✅ Reality: BMR varies less between individuals than most people think. A "slow" metabolism usually accounts for only 200-300 fewer calories—not thousands. Weight differences are more often due to activity levels and food intake.

❌ Myth: "Eating more meals speeds up metabolism"

âś… Reality: Meal frequency doesn't significantly affect BMR. What matters is total daily calorie intake, not how many meals you split it into.

❌ Myth: "Certain foods dramatically boost metabolism"

âś… Reality: While some foods (like protein and spicy foods) have mild thermogenic effects, no food magically "speeds up" your metabolism enough to cause significant weight loss.

When to Recalculate Your BMR

Your BMR changes as your body changes. Recalculate every:

  • 10-15 pounds of weight change
  • Significant change in muscle mass
  • Every 5-10 years as you age
  • After pregnancy or major illness
  • When your current calorie target stops working