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Fitness Calculators Tool

BMR Calculator

Determine your Basal Metabolic Rate (BMR) to find out how many calories you burn at complete rest using Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle.

Parameters

years
cm
kg
%
Calculated Results

Formula & Math

How this calculation works under the hood:

Mifflin-St Jeor: BMR = 10 * Weight (kg) + 6.25 * Height (cm) - 5 * Age (years) + s (where s = +5 for males, -161 for females). Harris-Benedict (Revised): BMR = 13.397 * Weight (kg) + 4.799 * Height (cm) - 5.677 * Age (years) + 88.362 (males) OR 9.247 * Weight (kg) + 3.098 * Height (cm) - 4.330 * Age (years) + 447.593 (females). Katch-McArdle: BMR = 370 + 21.6 * LBM (Lean Body Mass in kg).

Worked Example

Real-world scenario walk-through:

For a 25-year-old male, 175 cm tall, weighing 70 kg (15% body fat): - Mifflin: 10*70 + 6.25*175 - 5*25 + 5 = 1,674 kcal/day - Harris-Benedict: 88.362 + 13.397*70 + 4.799*175 - 5.677*25 = 1,724 kcal/day - Katch-McArdle (LBM = 59.5 kg): 370 + 21.6 * 59.5 = 1,655 kcal/day.

Calculation Architecture

Every calculator follows the same four-stage pattern: normalize the inputs, apply the selected formula, compute supporting values, and classify the result against a practical benchmark.

  1. 1. Normalize units and defaults Convert metric and imperial values into a consistent calculation base and apply the configured default values if a field is untouched.
  2. 2. Select the best formula Many tools expose several scientific models so you can compare outputs instead of relying on one narrow estimate.
  3. 3. Compute supporting metrics Secondary outputs such as categories, healthy ranges, or maintenance targets make the result easier to apply in real life.
  4. 4. Interpret the number Use the result as a decision aid, then compare it with the reference ranges and FAQs below for context.

Input Reference

Input Default Bounds Role
Formula Type
Selection
 mifflin Method-dependent Chooses the method or activity tier.
Gender
Selection
 male Method-dependent Chooses the method or activity tier.
Age
Numeric field
 25 15 to 100 years Feeds the core formula and result classification.
Height
Numeric field
 175 / 69 100 to 250 cm / 39 to 98 inches Feeds the core formula and result classification.
Weight
Numeric field
 70 / 154 30 to 300 kg / 60 to 660 lbs Feeds the core formula and result classification.
Body Fat % (Katch-McArdle only)
Numeric field
 15 2 to 70 % Feeds the core formula and result classification.

Formula Breakdown

The calculator can expose one or more formula paths. When multiple equations are available, compare them to understand the spread in the estimate.

Mifflin-St Jeor
BMR = 10 * Weight (kg) + 6.25 * Height (cm) - 5 * Age (years) + s (where s = +5 for males, -161 for females).
Harris-Benedict (Revised)
BMR = 13.397 * Weight (kg) + 4.799 * Height (cm) - 5.677 * Age (years) + 88.362 (males) OR 9.247 * Weight (kg) + 3.098 * Height (cm) - 4.330 * Age (years) + 447.593 (females).
Katch-McArdle
BMR = 370 + 21.6 * LBM (Lean Body Mass in kg).

Worked Example

Step through the sample calculation line by line so the final answer is easy to audit.

  1. For a 25-year-old male, 175 cm tall, weighing 70 kg (15% body fat):
  2. Mifflin: 10*70 + 6.25*175 - 5*25 + 5 = 1,674 kcal/day
  3. Harris-Benedict: 88.362 + 13.397*70 + 4.799*175 - 5.677*25 = 1,724 kcal/day
  4. Katch-McArdle (LBM = 59.5 kg): 370 + 21.6 * 59.5 = 1,655 kcal/day.

Understanding BMR Calculator

Basal Metabolic Rate (BMR) measures the minimal energy required to maintain vital physiological processes in a post-absorptive state, such as breathing, circulation, cell production, and temperature regulation. The Mifflin-St Jeor equation is recommended by the Academy of Nutrition and Dietetics as it predicts resting metabolic rate within 10% of indirect calorimetry measurements for 82% of healthy adults. However, if your body fat is known, the Katch-McArdle formula provides a more customized output because it scales directly with Lean Body Mass (LBM), which is metabolically more active than adipose tissue.

How to use the fitness result

Fitness calculators work best when you track trends, not just single-day numbers. The goal is to turn the output into a training, nutrition, or body-composition decision.

  • Recheck after a meaningful training block or bodyweight change.
  • Use the result alongside performance, recovery, and waist or body-fat trends.
  • Compare multiple formulas when the calculator offers more than one estimate.

For this calculator in particular, use the output as a practical benchmark for training age, body composition, and benchmark comparisons. If the result looks off, check measurement technique first, then formula choice, then the unit mode.

As a rule, recalculate after a meaningful change in training load, diet, sleep, bodyweight, or performance. That keeps the number relevant without chasing noise.

FAQs

How is BMR different from TDEE? +

BMR calculates your baseline caloric burn at complete rest to keep organs functioning. TDEE (Total Daily Energy Expenditure) adds BMR to the thermic effect of food (digestion) and physical activity levels.

Which BMR formula is the most accurate? +

For individuals with average body composition, Mifflin-St Jeor is the clinical standard. For highly muscular individuals or those with significant body fat, the Katch-McArdle equation is more accurate because it isolates lean body mass.

How often should I recalculate bmr? +

Recalculate whenever your bodyweight, training volume, recovery status, or goal changes enough to move the estimate. For most users, that means every 1 to 4 weeks depending on the calculator and the speed of change.

What should I do if this estimate seems too high or too low? +

Check your measurement inputs, confirm the unit mode, and compare the result against a second formula or a real-world trend. This is especially important for training age, body composition, and benchmark comparisons.

Should I compare this number to athlete standards or my own trendline? +

Use both. Athlete standards tell you where you sit relative to the population, while your own trendline shows whether your training, sleep, and nutrition are actually moving in the right direction.

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