How body fat is estimated
None of these methods measures fat directly. Each one is a regression equation: researchers measured body fat in a reference group with a laboratory method (underwater weighing or DEXA) and fitted a formula to simple measurements. Your result is the value the formula predicts for someone with your measurements.
Which one should a lifter use?
BMI-based formulas assume an average amount of muscle, so trained people with lots of lean mass get inflated results. Circumference and skinfold methods respond to your actual shape and are usually better for tracking a cut or bulk. Whatever you pick, use the same method every time — the trend over weeks is far more reliable than any single number.
Using your result
Lean body mass from this page can be used in lean-mass BMR equations (Katch-McArdle, Cunningham) in the TDEE calculator, in the FFMI calculator, and to set protein targets per kilogram of lean mass.
Frequently asked questions
Which body fat method is the most accurate at home?
Skinfold calipers used by a trained person and the U.S. Navy tape method both typically land within about 3–5 percentage points of lab methods such as DEXA for most adults. Consistency matters more than the method: measure the same way, at the same time of day, and track the trend.
How do I measure my waist and neck for the Navy method?
Measure the neck just below the larynx, sloping slightly down to the front. Men measure the waist horizontally at the navel; women at the narrowest point. Women also measure the hips at the widest point of the buttocks. Keep the tape snug but not compressing the skin, and don't suck in.
What is a healthy body fat percentage?
Commonly cited ranges (from the American Council on Exercise) place "fitness" levels at roughly 14–17% for men and 21–24% for women, with athletes lower. Essential fat is about 2–5% for men and 10–13% for women; going below these levels is associated with health risks.
Why do the methods give different results?
Each equation was developed on a different population with different reference methods. BMI-based estimates cannot distinguish muscle from fat, so they overestimate body fat in muscular people. Tape and skinfold methods use your actual body shape and are usually more useful for lifters.
What is Relative Fat Mass (RFM)?
RFM is a simple 2018 equation using only height and waist circumference. In the validation study it estimated whole-body fat percentage (measured by DEXA) more accurately than BMI in U.S. adults.
Sources & further reading
- Hodgdon JA, Beckett MB (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height . Naval Health Research Center, Report No. 84-11/84-29
- Jackson AS, Pollock ML (1978). Generalized equations for predicting body density of men . Br J Nutr 40(3):497–504 · doi:10.1079/BJN19780152
- Jackson AS, Pollock ML, Ward A (1980). Generalized equations for predicting body density of women . Med Sci Sports Exerc 12(3):175–181
- Deurenberg P, Weststrate JA, Seidell JC (1991). Body mass index as a measure of body fatness: age- and sex-specific prediction formulas . Br J Nutr 65(2):105–114 · doi:10.1079/BJN19910073
- Woolcott OO, Bergman RN (2018). Relative fat mass (RFM) as a new estimator of whole-body fat percentage — a cross-sectional study in American adult individuals . Sci Rep 8:10980 · doi:10.1038/s41598-018-29362-1