Body Fat Calculator
Use simple body measurements to estimate body fat percentage and lean-mass breakdown when you do not have access to a lab test.
How to use this body fat calculator
- Select sex
Choose male or female so the correct formula is applied.
- Enter weight
Enter your body weight in the weight field.
- Enter height
Enter your standing height in the height field.
- Enter circumferences
Measure and enter your neck and waist circumferences; if female, also enter hip circumference.
- Review results
Check your estimated body fat percentage along with the lean mass and fat mass breakdown.
How this body fat calculator works
This body fat calculator uses height and circumference measurements to estimate body fat percentage from a tape-measure formula. It is helpful when you want a more body-composition-focused estimate than BMI provides, especially if you track changes over time with the same measurement method.
Entered measurements are converted to inches internally.
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 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 A male who is 180 cm tall with a 85 cm waist and a 38 cm neck: %BF = 86.010 × log₁₀(85 − 38) − 70.041 × log₁₀(180) + 36.76 = 86.010 × 1.672 − 70.041 × 2.255 + 36.76 ≈ 143.9 − 157.9 + 36.76 ≈ 22.7% body fat. If he weighs 82 kg, estimated fat mass is about 18.6 kg and lean mass is about 63.4 kg.
A male who is 71 in tall with a 33.5 in waist and a 15 in neck: %BF = 86.010 × log₁₀(33.5 − 15) − 70.041 × log₁₀(71) + 43.23 = 86.010 × 1.267 − 70.041 × 1.851 + 43.23 ≈ 109.0 − 129.6 + 43.23 ≈ 22.6% body fat. If he weighs 181 lb, estimated fat mass is about 40.9 lb and lean mass is about 140.1 lb.
A female who is 168 cm tall, weighs 65 kg, and has a 34 cm neck, 72 cm waist, and 98 cm hip would estimate body fat at roughly 25.3%. That gives an estimated fat mass of about 16.4 kg and lean mass of about 48.6 kg, placing her within the commonly cited healthy range for women.
A male who is 175 cm tall, weighs 90 kg, and has a 40 cm neck and 95 cm waist would estimate body fat at roughly 26.5%. That gives an estimated fat mass of about 23.9 kg and lean mass of about 66.1 kg, suggesting that a meaningful portion of his weight is fat tissue rather than muscle.
- ✓ Measurement quality matters a lot, so inconsistent tape placement can change the result more than people expect.
- ✓ The estimate is based on the U.S. Navy circumference method, a practical field formula, not a direct body-composition test such as DEXA or hydrostatic weighing.
- ✓ Trends over time are often more useful than one isolated result.
- ✓ The formula was validated primarily on military populations and may be less accurate at extreme body-fat levels.
- Take measurements under similar conditions each time, ideally at the same time of day, to improve comparability.
- Use the result as a practical estimate and pair it with other markers like strength, waist trend, and health guidance when needed.
- The U.S. Navy method tends to be most accurate in the 10–35% body fat range for men and 18–40% for women.
- Hodgdon, J.A. & Beckett, M.B., 'Prediction of Percent Body Fat for U.S. Navy Men and Women from Body Circumferences and Height,' Naval Health Research Center, Report No. 84-29, 1984
- U.S. Department of Defense, DoD Instruction 1308.3 — DoD Physical Fitness/Body Composition Program
- Friedl, K.E. et al., 'Comparison of Circumference-Based Body Fat Estimation with Hydrostatic Weighing,' Military Medicine, 1992
What is body fat percentage?
Body fat percentage is the proportion of your total body weight that is made up of adipose (fat) tissue. It is a more informative metric than body weight alone because two people at the same weight can have very different amounts of muscle and fat. Essential fat — the minimum needed for normal physiological function — is roughly 2 to 5 percent in men and 10 to 13 percent in women. Athletes often carry 6 to 13 percent (men) or 14 to 20 percent (women), while ranges commonly described as healthy for the general population sit around 14 to 24 percent for men and 21 to 31 percent for women. Values above those ranges are associated with increased risk for metabolic conditions, though individual health depends on many factors beyond a single number. Tracking body fat percentage over time can reveal changes in body composition that scale weight alone would miss, such as gaining muscle while losing fat.
How to take accurate tape measurements
The accuracy of a circumference-based body fat estimate depends almost entirely on how consistently you take the measurements. For the neck, wrap the tape just below the larynx (Adam's apple) and keep it level around the circumference without compressing the skin. For the waist, men should measure at the navel while standing relaxed with a normal breath; women should measure at the narrowest point of the torso. For the hip measurement required in the female formula, place the tape at the widest point of the buttocks. In all cases, keep the tape snug but not tight, ensure it is horizontal and not twisted, and take two readings to confirm consistency. Measure at the same time of day under similar conditions — morning before eating is a common choice — to reduce variability from bloating or hydration changes.
Body fat calculator FAQs
Is this more useful than BMI?
It can be, because it attempts to estimate body composition rather than relying only on height and weight.
Why do tape measurements matter so much?
Because the formula depends directly on those measurements, even small errors in neck, waist, or hip placement can move the result noticeably.
Can I compare results over time?
Yes. The calculator is often most useful for tracking trends when you measure consistently from week to week or month to month.
Is this as accurate as a body scan?
No. It is a practical estimate, not a laboratory-grade body-composition test.
Why does the formula differ by sex?
Men and women store fat in different patterns. The female formula adds hip circumference because women typically carry more subcutaneous fat around the hips and thighs, which changes the relationship between circumferences and body fat.