fitness performance tool

BMR Calculator

Calculate your Basal Metabolic Rate (BMR) to understand how many calories your body burns at complete rest.

Calculate your rest metabolic rate using multiple scientific formulasPrecise Metabolic Math
Enter your body fat ratio to compute the lean-mass driven Katch-McArdle Formula.

Results & Comparison

BMR Comparisons

Metabolic Baseline Ready

Provide your age, height, and weight to generate and compare rest calorie expectations automatically.

What is Basal Metabolic Rate (BMR)?

Your Basal Metabolic Rate (BMR) represents the absolute minimum amount of energy (expressed in kilocalories per day) that your body requires to preserve life-sustaining functions while at complete physiological rest, in a temperate climate, and in a post-absorptive state (12 hours of fasting). These mandatory operations include cardiovascular circulation, neurological processes, respiratory contraction, metabolic waste filtration, and cellular division.

While BMR represents your metabolic rate under highly specific rest constraints, resting energy expenditure (REE) is often used interchangeably in clinical contexts. Approximately 60% to 75% of your Total Daily Energy Expenditure (TDEE) is governed strictly by your rest baseline, making your BMR the foundational element in calculating accurate caloric targets for weight loss, maintenance, or muscle development.

Clinical Formulas Discussed

1. Mifflin-St Jeor Equation (1990)Considered the gold standard by dietitians and clinical institutions, Mifflin-St Jeor is highly precise for modern populations. It calculates resting metabolic cost based on weight, height, age, and biological gender.
2. Harris-Benedict (Original 1918 & Revised 1984)The Harris-Benedict model is one of the oldest predictive tools. While the 1918 original had minor demographic skewing, the Roza and Shizgal revision in 1984 corrected these parameters, aligning its accuracy closely to modern standards.
3. Katch-McArdle FormulaUnlike height/weight models, Katch-McArdle predicts BMR entirely based on Lean Body Mass. Since adipose tissue is far less metabolically active than muscle tissue, individuals with low body fat or extreme muscularity find this formula significantly more accurate.

Methodology & Formula: Mifflin-St Jeor Equation

The Mifflin-St Jeor equation is the current gold standard for predicting resting energy expenditure. • Men: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) + 5 • Women: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age in years) - 161

Standard Reference Calculations

30-year-old Male

Inputs: Weight: 80 kg, Height: 180 cm, Age: 30
Output: BMR = 1,780 kcal/day

25-year-old Female

Inputs: Weight: 60 kg, Height: 165 cm, Age: 25
Output: BMR = 1,356 kcal/day

Frequently Asked Questions

Get answers to common queries based on clinical literature and fitness research.

BMR is the minimum number of calories your body needs to survive and perform basic, life-sustaining functions (such as breathing, circulation, cell production, and nutrient processing) while in a resting state.

To lose weight, you must consume fewer calories than your Total Daily Energy Expenditure (TDEE). Since TDEE is your BMR multiplied by your physical activity level, knowing your BMR is the starting point. You should never consume fewer calories than your BMR without medical supervision.

Yes, BMR generally decreases as you age. This is primarily due to a natural loss of lean muscle mass (sarcopenia) and a gradual increase in fat tissue proportion, which is less metabolically active.

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