Body Fat from BMI
Science-backed body composition analysis. Estimate your fat percentage using your BMI score and age.
This estimate uses the Deurenberg formula, which factors in your BMI, age, and gender. While not as accurate as a DEXA scan, it provides a reliable proxy for tracking fat-to-muscle trends over time.
Can You Truly Calculate Body Fat from BMI?
Body Mass Index (BMI) is a simple measure of your weight relative to your height. While it's a great tool for population studies, it lacks the ability to distinguish between muscle, bone, and fat. However, researchers have developed mathematical formulas—like the Deurenberg equation—that can estimate Body Fat Percentage with a surprising degree of accuracy for the general population.
Our Body Fat Percentage from BMI tool uses these scientific models to help you go one step deeper into your health profile. By factoring in your age and gender (which heavily influence body composition), we can turn a basic BMI score into a meaningful estimate of your actual body fatness.
Why does body fat matter more than weight? Excess adipose tissue, particularly visceral fat around the abdomen, is more directly linked to chronic diseases like Type 2 diabetes and heart disease than total body weight alone. A "skinny fat" individual might have a normal BMI but a dangerously high body fat percentage.
Use this estimate as a guideline. If you are a high-level athlete or have an unusual body type, we recommend following up with more direct measurements like skinfold calipers or bioelectrical impedance.
Estimated Fat % by BMI Score
| BMI Score | Est. Fat % (Men) | Est. Fat % (Women) |
|---|---|---|
| 18.5 - 20 | ~8-12% | ~15-20% |
| 21 - 23 | ~13-17% | ~21-25% |
| 24 - 26 | ~18-22% | ~26-30% |
| 27 - 29 | ~23-27% | ~31-35% |
| 30+ | ~28%+ | ~36%+ |
The Deurenberg Formula
Developed in 1991, the formula used here is:Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × Gender) − 5.4
(Gender: Male = 1, Female = 0)
"Tracking your fat percentage is a better predictor of health longevity than tracking weight alone."
Body Composition FAQ
Is a lower body fat always better?
No. The body needs "essential fat" for hormone production and vitamin absorption. For men, anything below 5% is dangerous; for women, anything below 12-15% can cause severe health complications.
How accurate is this estimate?
For most adults, the estimate is accurate within 3-5%. However, it significantly overestimates fat for muscular athletes and may underestimate fat for seniors with low muscle mass.
Does age affect body fat?
Yes. As you age, your body naturally tends to replace muscle mass with fat (sarcopenia). Even if your weight stays the same, your body fat percentage will naturally increase as you get older.
Why is female body fat higher?
Women are biologically designed to carry more fat for reproductive health, lactation, and hormonal balance. A "healthy" body fat for a woman is comparable to an "overweight" body fat for a man.