What is BMR and why does it matter?

BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — breathing, circulation, cell repair, temperature regulation. It accounts for 60–75% of total daily calorie burn. Knowing your BMR lets you set accurate calorie targets: eat below BMR × activity factor to lose weight, at maintenance to hold weight, or above to gain muscle.

Which BMR formula is most accurate — Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle?

Mifflin-St Jeor is considered the most accurate for average adults (within 10% for 80% of people). Harris-Benedict tends to overestimate by 5–15%. Katch-McArdle is the most accurate if you know your body fat percentage, because it calculates BMR from lean mass rather than total weight — making it ideal for athletes.

Does muscle mass increase BMR?

Yes. Muscle tissue burns approximately 13 kcal/kg/day at rest vs 4.5 kcal/kg/day for fat tissue. A person with 60 kg of lean mass has a meaningfully higher BMR than someone with 45 kg of lean mass at the same total weight. This is the main metabolic advantage of strength training.

How does BMR change during a diet?

BMR decreases during caloric restriction — your body adapts by reducing energy expenditure (metabolic adaptation). Studies show BMR can drop 10–15% below predicted levels after prolonged dieting. This is why weight loss plateaus occur and why diet breaks or refeeds help. Maintaining protein intake and resistance training minimizes this effect.

Why do men have higher BMR than women?

Men typically have 10–15% higher BMR than women of the same height, weight, and age. The primary reason is body composition: men have more muscle mass and less fat tissue on average. The Mifflin-St Jeor formula accounts for this with different constants for men and women.

How accurate are the results?

Our calculators use industry-standard formulas verified against academic sources and professional tools. Results are for informational and educational purposes — always verify important financial, health, or technical decisions with a qualified professional.

Does Calculators Point store my data?

No. All calculations run entirely in your browser. Your inputs are never transmitted to any server, logged, or stored — complete privacy by design.

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Free BMR Calculator Online

Mifflin vs Harris-Benedict with TDEE at all 5 activity levels

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest — the minimum energy required to keep your heart beating, lungs breathing, and organs functioning. This calculator computes your BMR using both the Mifflin-St Jeor and Harris-Benedict equations side by side, and then projects your TDEE across five activity levels so you can identify the right calorie target for your lifestyle.

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Frequently Asked Questions

✍️ Reviewed by the Calculators Point Editorial Team · Formulas cross-verified against academic and professional sources🗓️ Last updated: June 2026

About the BMR Calculator

BMR represents the largest portion of your total energy expenditure — typically 60–75% of the calories you burn each day. Even while sleeping, your body is consuming energy for cellular repair, temperature regulation, and organ function.

The Mifflin-St Jeor equation, developed in 1990, is validated against indirect calorimetry data and is considered the current gold standard for BMR estimation. The Harris-Benedict formula (1919, revised 1984) is still widely used but tends to overestimate BMR by about 5–10% in most populations.

Both formulas use only height, weight, age, and sex — which means they cannot account for muscle-to-fat ratio. If you have an unusually high or low muscle mass, your actual BMR will differ from these estimates. Pair your BMR with an accurate activity multiplier to find your real maintenance calories.

Formula Used

Mifflin-St Jeor:

Men: BMR = 10×weight(kg) + 6.25×height(cm) - 5×age - 5

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

When Should You Use This?

The BMR Calculator is ideally suited for fitness enthusiasts, healthcare professionals, and individuals monitoring their health who need to perform quick, accurate calculations related to general calculations. Use this tool when you need to verify figures, compare different scenarios, or get a precise answer without manual computation errors.

What Does The Result Mean?

The calculated metrics provide a scientifically validated baseline for your health or fitness goals. While these numbers are highly accurate based on standard medical formulas, they should serve as a guide rather than a replacement for professional medical advice.

Example Calculation

BMR and TDEE for a 42-year-old woman

📥 Inputs

Age: 42
Sex: Female
Weight: 72 kg
Height: 163 cm

🔢 Calculation Steps

1Mifflin-St Jeor (female): (10 × 72) + (6.25 × 163) − (5 × 42) − 161
2= 720 + 1018.75 − 210 − 161 = 1,367.75 kcal/day
3Harris-Benedict (female): 655.1 + (9.563 × 72) + (1.850 × 163) − (4.676 × 42)
4= 655.1 + 688.5 + 301.5 − 196.4 = 1,448.7 kcal/day
5TDEE at lightly active (×1.375): Mifflin = 1,880 kcal | Harris-Benedict = 1,992 kcal

BMR is approximately 1,368–1,449 kcal. At a lightly active level, she needs about 1,880–1,990 kcal/day to maintain current weight. Mifflin is typically the more accurate of the two.

Limitations of this Calculator

Formulas are based on population averages and may not perfectly reflect individuals with extreme muscle mass or atypical body compositions.
Does not replace a physical examination or clinical diagnosis by a certified medical professional.
Calculations cannot account for underlying metabolic conditions or genetic factors that influence individual health metrics.

How to Use the BMR Calculator

1Enter your values into the BMR Calculator input fields above.
2Review the input labels to ensure you are using the correct units.
3Click the "Calculate" button to get your instant result.
4Use the step-by-step breakdown to understand how the result was calculated.
5Export or copy your result to use in reports or share with others.

Tips & Best Practices

Mifflin-St Jeor is considered the most clinically accurate BMR formula for most adults.
BMR accounts for 60-75% of total daily calories — your body burns most energy just staying alive.
Double-check your input units before calculating — using the wrong unit is the most common source of errors.
Bookmark this BMR Calculator for quick access next time you need it.
Use the share button to send your results to a colleague or save them for later reference.

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⚠️ Health Disclaimer: Results provided by this calculator are for informational and educational purposes only. They do not constitute medical advice. Always consult a qualified healthcare professional, doctor, or registered dietitian before making any health, fitness, or dietary decisions.

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