Two people can have exactly the same BMI and very different bodies. One might carry a lot of muscle; the other might carry more fat around the waist.
That is why body fat percentage is often discussed alongside BMI. Here is how the two compare and how to use them sensibly.
What each number measures
| BMI | Body fat percentage | |
|---|---|---|
| What it measures | Weight relative to height | Share of body weight that is fat |
| What you need | Height and weight | Tape measurements, a device or a scan |
| Distinguishes muscle from fat? | No | Yes (estimate) |
| Ease of use | Very easy | Easy to difficult, depending on method |
BMI: strengths and weaknesses
- Strengths: quick, free, consistent, and linked with health risk across large populations.
- Weaknesses: cannot tell muscle from fat, ignores where fat is stored, and can misclassify athletes, older adults and some ethnic groups.
Read more in What is BMI and how is it calculated?.
How body fat percentage is estimated
| Method | Notes |
|---|---|
| Tape measure (U.S. Navy method) | Uses neck, waist (and hip) measurements. Free and repeatable; accuracy depends on careful measuring. |
| Skinfold calipers | Measures skinfold thickness at several sites. Accuracy depends heavily on the tester’s skill. |
| Bioelectrical impedance scales | Convenient, but readings are affected by hydration, meals and exercise. |
| DEXA scan | Among the more accurate methods; also shows fat distribution. Cost and access are limiting. |
Typical body fat ranges
The American Council on Exercise (ACE) uses these general categories for adults:
| Category | Women | Men |
|---|---|---|
| Essential fat | 10 – 13% | 2 – 5% |
| Athletes | 14 – 20% | 6 – 13% |
| Fitness | 21 – 24% | 14 – 17% |
| Average | 25 – 31% | 18 – 24% |
| Obesity range | 32% and above | 25% and above |
Which should you use?
Neither number is perfect, and each answers a slightly different question. For most people, the most useful approach is to use them together:
- Use BMI as a quick screening check — the BMI calculator takes seconds.
- Add a waist measurement or body fat estimate to understand body composition.
- Track trends over time using the same method each time rather than focusing on a single reading.
- Remember that fitness, blood pressure, blood sugar and other markers matter too.
Try the calculators
Put this guide into practice with a free estimate.
Frequently asked questions
Is body fat percentage more accurate than BMI?
Body fat percentage tells you more about body composition, but home estimates have their own errors. BMI is simpler and more consistent. Used together they give a better picture than either alone.
Can I have a normal BMI but high body fat?
Yes. This is sometimes called “normal-weight obesity”. It is one reason a waist measurement or body fat estimate can be useful alongside BMI.
How often should I measure body fat?
Every four to eight weeks is plenty for most people. Measure under the same conditions each time and focus on the overall trend.
Methods and sources
- World Health Organization — Obesity and overweight fact sheet (BMI classification) (opens in a new tab)
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984.
- American Council on Exercise (ACE) — body-fat percentage categories