BMR Calculator

Calculate your Basal Metabolic Rate using the Mifflin-St Jeor equation — the most accurate formula for most people.

About BMR Calculator

Your Basal Metabolic Rate (BMR) represents the number of calories your body needs at complete rest to maintain vital functions — breathing, circulation, cell production, and nutrient processing. This calculator uses the Mifflin-St Jeor equation, widely considered the most accurate formula for estimating BMR in the general population, and compares it against the Harris-Benedict equation for reference.

Mifflin-St Jeor Formula

Male: BMR = 10W + 6.25H - 5A + 5 | Female: BMR = 10W + 6.25H - 5A - 161. Developed in 1990 and validated across multiple studies.

Dual Formula Comparison

Compare Mifflin-St Jeor with the classic Harris-Benedict equation side by side to see how different formulas estimate your resting metabolism.

Flexible Units

Enter weight in kilograms or pounds and height in centimeters or feet/inches — the calculator handles the conversion automatically.

Build Your Nutrition Plan

Your BMR is the foundation for calculating Total Daily Energy Expenditure (TDEE). Use it alongside our TDEE and Macro calculators for a complete picture.

📋 Common Use Cases

Track Your Health Progress

Monitor changes in your health metrics over weeks and months. Regular tracking helps you see trends, stay motivated, and adjust your fitness or nutrition plan based on real data.

Set Realistic Fitness Goals

Use your calculated metrics to set achievable weight, nutrition, and fitness targets. Understand your baseline numbers before starting any new diet or exercise program.

Professional Health Assessment

Healthcare professionals, personal trainers, and coaches can quickly compute client metrics during consultations without accessing specialized equipment or software.

Nutrition & Diet Planning

Use your results to plan meal portions, macronutrient targets, and daily calorie budgets. Combine multiple health calculators for a complete wellness picture.

🪜 How to Use This Tool

  1. Enter your body measurements
    Fill in the required fields — typically height, weight, age, and gender. Use the unit toggles if you prefer metric or imperial units.
  2. Add optional details if available
    Some calculators accept additional inputs like activity level, waist circumference, or body fat percentage for more precise results.
  3. Review your calculated metrics
    Your results appear instantly with clear labels and reference ranges. Color-coded indicators show where you fall on standard health classification scales.
  4. Track changes over time
    Bookmark the page and return periodically to recalculate. Comparing results over weeks and months reveals meaningful health trends.

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Frequently Asked Questions

Are these calculators really free?▼
Yes. All calculators on iluv.tools are completely free. No signup, no account, no credit card required. Every calculation runs instantly in your browser.
Is my data sent anywhere?▼
Absolutely not. All calculators are pure client-side JavaScript. Your numbers, dates, and inputs never leave your browser. No server processing, no tracking.
How accurate are these calculators?▼
Calculators use standard mathematical formulas with double-precision floating point. Results match industry-standard financial and scientific calculations.
Can I use calculators on mobile?▼
Yes. All calculators work on mobile browsers (iOS Safari, Android Chrome) with responsive layouts.