BMR Calculator

Calculate your Basal Metabolic Rate


Evidence-Based Information

Based on scientific research and guidelines from leading health organizations

BMR Calculator: The Ultimate Guide to Your Basal Metabolic Rate

Use our free BMR calculator to discover your unique metabolic rate. Learn how to calculate BMR with formulas, understand low vs. high BMR, and get expert tips to optimize your metabolism.

The Ultimate Guide to BMR: What It Is, How to Calculate It, and What to Do Next

Ever wondered how many calories your body burns just to stay alive? That's your Basal Metabolic Rate (BMR). It's the foundational number for your entire health, fitness, and nutrition strategy.

Understanding your BMR is the first and most critical step in managing your weight, building muscle, or simply living a healthier life. But what is it really? How is it calculated? And most importantly, what do you do with that number?

This comprehensive guide will answer all your questions. We'll dive deep into the science behind BMR, show you the exact formulas, and provide actionable advice based on your results.

Ready to find your number? Use our simple, science-backed BMR calculator to get your personalized result in seconds.

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📈 What is BMR (Basal Metabolic Rate)?

Your Basal Metabolic Rate (BMR) is the minimum number of calories your body needs to perform its most basic, life-sustaining functions if you were to rest in a temperature-neutral environment for 24 hours.

Think of it as the energy your body spends on:

  • Breathing
  • Circulating blood
  • Brain and nerve function
  • Cell growth and repair
  • Maintaining body temperature

It's the "cost of living" for your body, completely separate from the calories you burn during exercise or even digestion.

BMR vs. RMR: What's the Difference?

You'll often see BMR used interchangeably with RMR (Resting Metabolic Rate). While very similar, there's a slight technical difference:

BMR (Basal Metabolic Rate)

  • • Measured under strict lab conditions
  • • After 8-hour fast
  • • Complete physical rest
  • • Temperature-neutral environment
  • • More precise measurement

RMR (Resting Metabolic Rate)

  • • Less restrictive measurement
  • • Practical everyday conditions
  • • Typically 3-10% higher than BMR
  • • More commonly used in fitness
  • • What our calculator estimates

🧮 How to Calculate BMR: The Formulas

While our calculator is the easiest way to find your BMR, it's helpful to understand the science behind it. The most widely accepted formulas are the Mifflin-St Jeor equation (considered the most accurate) and the Harris-Benedict equation (an older, but still reliable, classic).

The Mifflin-St Jeor Equation (The Modern Standard)

Developed in 1990, this formula is now considered the gold standard for predicting BMR in healthy adults.

For Men:

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5

For Women:

BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

The Harris-Benedict Equation (The Classic Formula)

This formula was developed in 1919 and later revised. It's still widely used but may slightly overestimate BMR, especially in overweight individuals.

For Men (Revised):

BMR = 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) - (5.677 × age in years)

For Women (Revised):

BMR = 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) - (4.330 × age in years)

Not a fan of math? Let us do the work for you.

Try our easy BMR Calculator now!

BMR Calculation Examples

Let's put the Mifflin-St Jeor formula into action.

Example 1: Sarah

  • Gender: Female
  • Age: 35 years
  • Weight: 70 kg (approx. 154 lbs)
  • Height: 168 cm (approx. 5' 6")

BMR = (10 × 70) + (6.25 × 168) - (5 × 35) - 161

BMR = 700 + 1050 - 175 - 161

BMR = 1,414 Calories/day

Example 2: David

  • Gender: Male
  • Age: 42 years
  • Weight: 85 kg (approx. 187 lbs)
  • Height: 180 cm (approx. 5' 11")

BMR = (10 × 85) + (6.25 × 180) - (5 × 42) + 5

BMR = 850 + 1125 - 210 + 5

BMR = 1,770 Calories/day

📊 Understanding Your BMR: Low vs. High

Your BMR result isn't just a number; it's a reflection of your body's unique metabolic engine. It can be influenced by several factors, leading to a "high" or "low" BMR relative to the average.

Factors That Increase BMR

Muscle Mass ↑↑↑
Larger Body Size ↑↑
Male Gender ↑↑
Younger Age ↑
Cold Environment ↑

Factors That Decrease BMR

Low Muscle Mass ↓↓↓
Older Age ↓↓
Female Gender ↓
Crash Dieting ↓↓
Thyroid Issues ↓↓

What Factors Affect BMR?

Factor How It Affects Your BMR Impact Level
Muscle Mass The more muscle you have, the higher your BMR. Muscle is metabolically active and burns calories even at rest. High
Age BMR naturally decreases with age, roughly 2-3% per decade after age 30, often due to muscle loss. Medium
Body Size Taller and heavier individuals typically have a higher BMR because they have a larger body to support. Medium
Gender Men generally have a higher BMR than women, primarily because they tend to have more muscle mass and less body fat. Medium
Hormones Thyroid hormones are a primary regulator. An overactive thyroid increases BMR, while an underactive one slows it down. Variable

What Does a "High BMR" Mean?

A "high" BMR means your body burns more calories at rest than the average person of your age, height, and gender.

Common Causes:

  • Higher-than-average muscle mass (from strength training)
  • Genetics
  • Sometimes an overactive thyroid

What it Means for You: You can eat more calories without gaining weight. This is often seen as an advantage for weight management, but it also means you need more fuel to maintain your weight or build new muscle.

What Does a "Low BMR" Mean?

A "low" BMR means your body burns fewer calories at rest.

Common Causes:

  • Lower-than-average muscle mass
  • Very sedentary lifestyle
  • Advanced age
  • An underactive thyroid (hypothyroidism)

What it Means for You: You may gain weight more easily and need to be more mindful of your calorie intake. This is not a permanent sentence. The most effective way to combat a low BMR is to change your body composition.

🏃‍♀️ BMR is Not Your Total Calorie Burn: Understanding TDEE

This is the most common mistake people make. Your BMR is NOT the number of calories you should eat in a day.

You need to account for your activity. This is called your Total Daily Energy Expenditure (TDEE).

The formula is simple:

TDEE = BMR × Activity Factor

Where Your Calories Go: TDEE Breakdown

BMR (60-70%) - Basal Metabolism
Activity (15-30%) - Exercise & Movement
TEF (10%) - Food Digestion
Activity Level Description Multiplier
Sedentary Little or no exercise (e.g., desk job) 1.2
Lightly Active Light exercise/sports 1-3 days/week 1.375
Moderately Active Moderate exercise/sports 3-5 days/week 1.55
Very Active Hard exercise/sports 6-7 days/week 1.725
Extremely Active Very hard exercise, physical job, or 2x/day training 1.9

Example (using Sarah from before):

Sarah's BMR: 1,414 Calories

Her Activity Level: Moderately Active (works a desk job but goes to the gym 4 days/week)

Her TDEE = 1,414 × 1.55 = 2,192 Calories

This 2,192 is Sarah's "maintenance" level—the number of calories she needs to eat to maintain her current weight.

💡 Recommendations: What to Do With Your BMR & TDEE

Now you have the data. Here's how to use it.

Weight Loss

You must be in a caloric deficit.

Strategy:

Subtract 300-500 calories from your TDEE (not your BMR).

Example:

If your TDEE is 2,200, aim for 1,700-1,900 calories per day.

Pro-Tip: Never eat below your BMR for extended periods.

Weight Gain (Muscle)

You must be in a caloric surplus.

Strategy:

Add 250-500 calories to your TDEE.

Example:

If your TDEE is 2,200, aim for 2,450-2,700 calories per day.

Pro-Tip: Prioritize protein (1.6-2.2g per kg of body weight).

Weight Maintenance

You need caloric balance.

Strategy:

Eat at your TDEE level.

Example:

If your TDEE is 2,200, that is your target.

Pro-Tip: Focus on weekly trends, not daily numbers.

How to Increase Your BMR (Yes, You Can!)

While you can't change your genetics or your age, you can absolutely influence your BMR. The single most effective way is to build muscle.

Start Strength Training

This is non-negotiable. Lifting weights creates micro-tears in your muscle, which your body repairs and builds back stronger.

Eat Enough Protein

Your body needs protein to build and repair that muscle. Aim for protein with every meal.

Stay Active (NEAT)

NEAT stands for Non-Exercise Activity Thermogenesis. It's all the movement you do outside of the gym.

Avoid Crash Diets

Severely slashing calories for a long time teaches your body to become "efficient" with less, which means your BMR drops.

Take Control of Your Metabolism

Understanding your Basal Metabolic Rate is the key to unlocking your health goals. It removes the guesswork and empowers you to create a nutrition plan that is built specifically for your body.

Your BMR is the starting line. Your TDEE is your daily target. And your goal (loss, gain, or maintenance) is the strategy.

Ready to find your starting line?

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Medical Disclaimer

This BMR Calculator is an educational tool designed to provide general information and should not be considered medical advice. The results are based on standard guidelines and may not account for individual health circumstances, genetic factors, or concurrent medical conditions. Always consult with a qualified healthcare professional for proper interpretation of your results, personalized target goals, and treatment recommendations. Do not make changes to medications or treatment plans without consulting your physician.

Sources and References

The information and calculations on this page are based on established guidelines and research from leading health organizations. We are committed to providing accurate and transparent information.

Frequently Asked Questions (FAQ)

What is the most accurate BMR formula?

The Mifflin-St Jeor equation is currently considered the most accurate for estimating BMR in healthy adults.

Can I increase my BMR?

Yes. Building lean muscle mass through strength training is the most effective way to permanently increase your BMR.

Is it safe to eat below my BMR?

Generally no. Eating below BMR for long periods can slow metabolism and cause muscle loss.