BMI & Body Fat Calculator
Calculate your Body Mass Index and estimate body fat percentage using the U.S. Navy method. Get a complete body composition analysis instantly in your browser.
BMI Categories
< 18.5
18.5 - 24.9
25 - 29.9
30+
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About BMI & Body Fat Calculation
Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is weight in kilograms and m² is height in metres squared. BMI provides a reliable indicator of body fatness for most people and is used to screen for weight categories that may lead to health problems.
Body fat percentage is a superior metric to BMI alone. The U.S. Navy method estimates body fat using circumference measurements. For men, it uses neck and waist measurements. For women, it also uses hip measurements. This method provides a reasonable estimate without expensive equipment like DEXA scans.
Lean Body Mass (LBM) represents everything in your body except fat, including muscles, bones, organs, and water. It is calculated by subtracting fat mass from total body weight. Understanding your LBM helps with fitness planning and nutritional goals.
Body Fat Categories
For men: Essential fat 2-5%, Athletes 6-13%, Fitness 14-17%, Average 18-24%, Obese 25%+. For women: Essential fat 10-13%, Athletes 14-20%, Fitness 21-24%, Average 25-31%, Obese 32%+.
Frequently Asked Questions
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by your height in meters squared (kg/m²). It provides a general indication of whether you are underweight, normal weight, overweight, or obese.
What is the Navy method for body fat?
The Navy method estimates body fat percentage using measurements of the neck, waist, and hips (for women). It was developed by the US Navy and provides a reasonable estimate without specialized equipment.
Is BMI accurate for everyone?
BMI has limitations. It does not distinguish between muscle and fat mass, so athletes or muscular individuals may have a high BMI despite low body fat. Combining BMI with body fat percentage gives a more complete picture.
What is lean body mass?
Lean body mass is your total body weight minus fat mass. It includes muscles, bones, organs, and water. It is calculated as: Weight × (1 - body fat percentage / 100).
Last updated: June 2026