BMI & Fitness Level Calculator
Calculate your BMI and estimate your fitness level from body fat. Enter your weight, height, age, and sex, and this calculator returns your BMI, an estimated body-fat percentage using the Deurenberg formula, and a fitness category.
Formula
BMI = Weight / Height²; Body Fat% = 1.20×BMI + 0.23×Age − 16.2 (male) / −5.4 (female) [Deurenberg]
- BMI is your weight in kg divided by height in metres squared.
- Body fat is estimated with the Deurenberg formula, which adjusts for age and sex: men subtract 16.2 and women subtract 5.4.
- The fitness category is based on the estimated body-fat percentage, not BMI alone.
- Body fat gives a fuller picture than BMI because it separates lean mass from fat.
- These are estimates — methods like calipers or DEXA scans give more precise body-fat readings.
30-year-old man, 75 kg, 175 cm
Inputs
- Weight: 75 kg
- Height: 175 cm
- Age: 30 years
BMI = 75 ÷ 1.75² ≈ 24.5 (normal). Estimated body fat is about 19%, placing this person in a fit-to-acceptable range.
Frequently asked questions
How is body fat estimated here?
It uses the Deurenberg formula, which predicts body-fat percentage from BMI, age, and sex. It is a quick estimate, not a direct measurement.
Why combine BMI with body fat?
BMI alone cannot tell muscle from fat. Adding a body-fat estimate gives a better sense of fitness, especially for active people.
What body-fat range is considered fit?
Roughly 14–17% for men and 21–24% for women is often labelled fit, though healthy ranges vary by age and goals.
Is the Deurenberg estimate accurate?
It is within a few percent for most people but can be off for very muscular or very lean individuals. Use it as a guide.
How can I measure body fat more precisely?
Skinfold calipers, bioelectrical impedance scales, and DEXA scans all give more accurate readings than formula-based estimates.