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Mifflin-St Jeor: BMR = (10 × W) + (6.25 × H) - (5 × Age) + s

BMR (Basal Metabolic Rate) Calculator

Calculate baseline calories burned at complete rest using Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle equations.

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Formula & Mathematical Method

This calculator uses standard deterministic mathematical algorithms to process user inputs in real time. Calculations are performed client-side for maximum speed and privacy.

Reviewed by Metabolic Health & Exercise Physiology Board
Checked for AccuracyLast Reviewed: July 2026

Understanding Basal Metabolic Rate (BMR) & Daily Resting Energy

Theoretical background and practical computational guidance

Basal Metabolic Rate (BMR) represents the absolute baseline number of calories your body burns at complete rest during a 24-hour period just to perform vital life-sustaining functions such as breathing, blood circulation, cellular repair, and brain activity.

BMR accounts for approximately 60% to 75% of a total human daily energy expenditure (TDEE). Factors influencing your BMR include lean muscle mass, biological sex, age, height, genetics, and thyroid hormone regulation.

Knowing your BMR is essential for creating structured nutritional goals. To lose fat or gain muscle effectively, daily caloric intakes are built by scaling your BMR with physical activity multipliers.

BMR Equations: Mifflin-St Jeor, Harris-Benedict & Katch-McArdleMathematical Standard
Mifflin (Male) = 10W + 6.25H - 5A + 5 | Mifflin (Female) = 10W + 6.25H - 5A - 161 | Katch-McArdle = 370 + 21.6 × LeanMass(kg)

Where W is weight in kilograms, H is height in centimeters, A is age in years, and LeanMass is total body mass minus body fat mass.

Worked Calculation Walkthrough & Analytical Steps

To evaluate a typical problem using the BMR (Basal Metabolic Rate) Calculator, identify your known baseline inputs, convert all measurements to congruent units, and apply the governing formula sequentially. Below is a structured breakdown of the computational workflow:

  1. Data Ingestion & Unit Harmonization: Enter the primary parameters into the input fields. If working with mixed metric or imperial dimensions, use the unit selector above to align scales.
  2. Intermediate Term Evaluation: The algorithm evaluates inner parentheses, rate exponents, and coefficient ratios in strict compliance with mathematical precedence.
  3. Final Transformation & Precision Rounding: The final numerical figure is determined, formatted to user-selected decimal precision, and mapped against relevant diagnostic or diagnostic thresholds.

Key Insights & Operational Tips

  • BMR is the caloric cost of staying alive at complete physical rest.
  • Increasing lean muscle mass through resistance training raises your resting BMR.
  • Never consume fewer total calories than your BMR for extended periods without medical supervision.

Frequently Asked Questions (FAQs)

Authoritative answers to common computational and formula questions

The Mifflin-St Jeor equation is clinically proven to be the most accurate for modern adults. If exact body fat percentage is known, the Katch-McArdle formula is even more precise.
BMR measures energy expended in a strictly controlled thermal and metabolic state upon waking. Resting Metabolic Rate (RMR) measures resting energy under slightly looser conditions and is typically 5-10% higher.

Authoritative Citations & Institutional References

Disclaimer & Methodological Transparency Notice

Medical Disclaimer: BMR calculations provide clinical estimates. Endocrine conditions (such as hypothyroidism) may alter actual metabolic rate.