Body fat percentage tells you how much of your weight is fat rather than muscle, bone and water, so it says more about health and fitness than weight or BMI alone. Essential fat is needed for hormones and organs; too much fat, especially around the waist, raises the risk of heart disease and diabetes. Lab methods such as DEXA are the most accurate, but tape and formula methods are free and good for tracking change.
How to use the Body Fat Calculator
- Sex
- Age
- Weight
- Height
- Method
- Neck circumference: Just below the larynx, tape sloping slightly down to the front.
- Waist circumference: Men: at the navel. Women: at the narrowest point.
- Hip circumference (women): Only used for women; widest part of the hips.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose a method. The US Navy method uses your height, neck and waist (plus hips for women) and is usually the most accurate of the three. The BMI method needs only height, weight, age and sex. Fat mass is weight × body fat %, and lean mass is the rest. Your result is compared with the ACE categories and with the Jackson & Pollock ideal body fat for your age.
Body fat categories (ACE)
| Category (ACE) | Women | Men |
|---|---|---|
| Essential fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | 32% and above | 25% and above |
Ideal body fat by age (Jackson & Pollock)
| Age | Women | Men |
|---|---|---|
| 20 | 17.7% | 8.5% |
| 25 | 18.4% | 10.5% |
| 30 | 19.3% | 12.7% |
| 35 | 21.5% | 13.7% |
| 40 | 22.2% | 15.3% |
| 45 | 22.9% | 16.4% |
| 50 | 25.2% | 18.9% |
| 55 | 26.3% | 20.9% |
Inputs explained
| Field | What to enter |
|---|---|
| Sex | Choose one: Male, Female |
| Age | In years |
| Weight | Units: kg, lb, st, g |
| Height | Units: cm, in, m, ft, mm |
| Method | Choose one: US Navy (tape measure), BMI method (Deurenberg), ADA (Gallagher) equation |
| Neck circumference | Units: cm, in, m, ft, mm. Just below the larynx, tape sloping slightly down to the front. |
| Waist circumference | Units: cm, in, m, ft, mm. Men: at the navel. Women: at the narrowest point. |
| Hip circumference (women) | Units: cm, in, m, ft, mm. Only used for women: widest part of the hips. |
What each result means
- Fat mass = [Weight]×[Body fat]÷100
- Lean mass = [Weight] – [Fat mass]
- Fat to lose to reach the ideal = max([Fat mass] – [Weight]×[Ideal body fat for your age (Jackson & Pollock)]÷100, 0)
Health note: this calculator is for education and screening only and is not a diagnosis or treatment advice. Discuss your results with a qualified clinician.
Formula
US Navy (inches): men %BF = 86.010·log₁₀(waist − neck) − 70.041·log₁₀(height) + 36.76
women %BF = 163.205·log₁₀(waist + hip − neck) − 97.684·log₁₀(height) − 78.387
BMI method (Deurenberg): %BF = 1.20·BMI + 0.23·age − 10.8·sex − 5.4 (sex: men 1, women 0)
ADA (Gallagher): %BF = 64.5 − 848/BMI + 0.079·age − 16.4·sex + 0.05·sex·age + 39.0·sex/BMI
Worked example
Inputs: Sex: Male; Age: 30 years; Weight: 80 kg; Height: 178 cm; Method: US Navy (tape measure); Neck circumference: 39 cm; Waist circumference: 88 cm; Hip circumference (women): 100 cm.
Results: Body fat = 18 %; Body fat category (ACE) = Average; Fat mass = 14.4 kg; Lean mass = 65.6 kg; Ideal body fat for your age (Jackson & Pollock) = 12.7 %; Fat to lose to reach the ideal = 4.3 kg.
Key terms
- Essential fat
- The minimum fat needed for normal body function.
- Lean mass
- Everything except fat: muscle, bone, organs and water.
- DEXA
- Dual-energy X-ray absorptiometry, a lab scan of body composition.
Frequently asked questions
What is a healthy body fat percentage?
For adults, about 14–24% for men and 21–31% for women is in the fitness to average range.
Which method is most accurate?
Of these, the US Navy tape method agrees best with lab methods (within about 3–4 percentage points). DEXA, hydrostatic weighing and air displacement are more accurate.
Why does my smart scale give a different number?
Bioimpedance scales are affected by hydration and food; use one method consistently to track trends.
Can body fat be too low?
Yes. Below essential levels (about 2–5% for men and 10–13% for women) hormones and organs suffer.
Sources
- 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
- Deurenberg P et al. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr, 1991
- Gallagher D et al. Healthy percentage body fat ranges. Am J Clin Nutr, 2000
- American Council on Exercise: Percent body fat norms
Guides on this topic
- BMI vs Body Fat Percentage: Which One Should You Track?: Two people with the same BMI can carry twice as much fat as each other. Here is what BMI and body fat each measure, and how to estimate body fat with a tape.