The Body Fat Calculator gives you a fast estimate of your body fat percentage using only your sex, age, weight and height — no calipers, scans or tape measure required. It is built for anyone who wants a quick check-in on body composition, whether you are starting a fitness plan, tracking progress between gym sessions, or simply curious how your number compares to healthy ranges for your sex and age group. Unlike scale weight alone, body fat percentage tells you how much of your mass is fat versus lean tissue (muscle, bone, organs and water), which is a far better signal of health and fitness than weight or BMI in isolation.
Select your sex, then enter your age in years, weight in kilograms and height in centimeters. The result updates instantly — no need to press calculate more than once unless you change a value. If you use imperial units, convert first: 1 inch = 2.54 cm and 1 pound = 0.4536 kg. For the most consistent tracking over time, measure yourself at the same time of day (ideally morning, before eating) and use the same scale.
This tool uses the Deurenberg equation, one of the most widely validated formulas for estimating body fat from BMI: Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × Sex) − 5.4, where Sex = 1 for male and 0 for female, and BMI = weight (kg) ÷ height² (m²). The formula captures two well-established patterns: body fat tends to rise with age even at a constant BMI, and women naturally carry a higher body fat percentage than men at the same BMI due to hormonal and physiological differences.
Example 1: A 30-year-old man, 70 kg, 175 cm. BMI = 70 ÷ 1.75² = 22.9. Body fat = (1.20 × 22.9) + (0.23 × 30) − 10.8 − 5.4 = 27.48 + 6.9 − 10.8 − 5.4 ≈ 18.2%, in the "fitness" range for men.
Example 2: A 45-year-old woman, 65 kg, 165 cm. BMI = 65 ÷ 1.65² = 23.9. Body fat = (1.20 × 23.9) + (0.23 × 45) − 0 − 5.4 = 28.66 + 10.35 − 5.4 ≈ 33.6%, within the "acceptable" range for women over 40.
Example 3: A 22-year-old man, 82 kg, 183 cm. BMI = 82 ÷ 1.83² = 24.5. Body fat = (1.20 × 24.5) + (0.23 × 22) − 10.8 − 5.4 = 29.4 + 5.06 − 10.8 − 5.4 ≈ 18.3%, similar to Example 1 despite a heavier frame — a reminder that BMI-based estimates reward height and muscle mass differently than raw weight.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | 25%+ | 32%+ |
Ranges adapted from the American Council on Exercise (ACE) body fat classification.
The Deurenberg formula estimates body fat from BMI, age and sex. It is an approximation, not a clinical measurement — methods like DEXA scans or hydrostatic weighing are more precise but far less accessible.
Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × Sex) − 5.4, where Sex is 1 for male and 0 for female. It was developed from a large population study correlating BMI, age and sex with body fat measured by underwater weighing.
Women naturally carry more essential fat than men (needed for hormonal and reproductive function), so the formula subtracts less for women (Sex=0 removes the 10.8 term) than for men.
No. Body fat below the "essential fat" range (2–5% for men, 10–13% for women) can impair hormone production, immune function and bone health. Healthy ranges exist for a reason.
Calipers and DEXA measure fat directly and are more accurate, but this BMI-based estimate is free, instant and a reasonable starting point when those tools are not available.
Once every 2–4 weeks is enough to see a meaningful trend. Checking daily mostly captures water-weight noise, not real changes in body composition.