BMI & BMR Calculator
A BMI & BMR Calculator computes your Body Mass Index with a color-coded WHO category scale, estimates Basal Metabolic Rate using Harris-Benedict and Mifflin-St Jeor equations, calculates TDEE across 5 activity levels, derives ideal weight from 4 medical formulas (Devine, Robinson, Miller, Hamwi), and estimates body fat via the U.S. Navy method — all with interactive SVG visualizations. Free, no sign-up required.
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What is a BMI & BMR Calculator?
A BMI & BMR Calculator is a tool that computes two key health metrics from your body measurements. Body Mass Index (BMI) classifies weight status using the WHO scale (Underweight < 18.5, Normal 18.5–24.9, Overweight 25–29.9, Obese ≥ 30). Basal Metabolic Rate (BMR) estimates the calories your body burns at rest, using validated equations like Harris-Benedict (revised 1984) and Mifflin-St Jeor (1990). Combined with activity multipliers, BMR produces your Total Daily Energy Expenditure (TDEE) — the estimated calories needed per day. This calculator also includes ideal weight estimation from four medical formulas (Devine, Robinson, Miller, Hamwi) and body fat percentage via the U.S. Navy circumference method.
How to Use This Calculator
- Select your unit system (Metric or Imperial) and enter your gender, age, height, and weight
- View your BMI result with WHO category classification on the color-coded scale bar
- Switch to the BMR & TDEE tab to see your daily calorie estimates at different activity levels
- Check the Ideal Weight tab to compare your weight against four medical formulas
- Use the Body Fat tab with waist, neck, and hip measurements for a body fat estimate
Frequently Asked Questions
What is the difference between BMI and BMR?
BMI (Body Mass Index) is a weight-to-height ratio that classifies your weight status (underweight, normal, overweight, obese). BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest over 24 hours to maintain basic functions like breathing, circulation, and cell repair. BMI indicates weight category, while BMR indicates metabolic energy needs.
Which BMR formula is more accurate: Harris-Benedict or Mifflin-St Jeor?
The Mifflin-St Jeor equation (1990) is generally considered more accurate for modern populations, as the original Harris-Benedict equation was developed in 1919. The revised Harris-Benedict (1984) is closer to Mifflin-St Jeor in accuracy. Both are shown so you can compare — for most people, the difference is 50-100 kcal/day.
Is BMI accurate for athletes and muscular people?
BMI does not distinguish between muscle and fat mass, so muscular individuals may have a high BMI despite being healthy. For athletes and bodybuilders, the Body Fat tab using the U.S. Navy method or other body composition measurements provides a more meaningful assessment than BMI alone.
How do I calculate my TDEE?
TDEE (Total Daily Energy Expenditure) equals your BMR multiplied by an activity factor. Sedentary (×1.2): desk job, little exercise. Lightly active (×1.375): light exercise 1-3 days/week. Moderately active (×1.55): moderate exercise 3-5 days/week. Active (×1.725): hard exercise 6-7 days/week. Very active (×1.9): intense exercise plus physical job. This calculator computes all five levels for easy comparison.