Body Fat Calculator
Estimate your body fat percentage with a tape measure using the U.S. Navy circumference method.
How to use the Body Fat Calculator
- Choose the sex.
- Choose the units.
- Enter the height – feet.
- Enter the height – inches.
- Enter the height.
- Enter the weight (for fat mass).
- Enter the weight (for fat mass).
- Enter the neck circumference and pick its unit – Just below the larynx (Adam's apple).
- Enter the waist circumference and pick its unit – Men: at the navel. Women: at the narrowest point.
- Enter the hip circumference and pick its unit – At the widest point of the buttocks.
- Press Calculate. The result updates automatically as you type, and you can switch the result unit at any time.
About the Body Fat Calculator
The U.S. Navy method estimates body fat from a few circumference measurements because fat around the waist increases its size relative to the neck. It was developed by the Naval Health Research Center and is still used for military fitness screening because it needs only a tape measure.
For best results, measure on bare skin in the morning, keep the tape level and snug without compressing the skin, and take each measurement two or three times. The method is typically within about 3–4 percentage points of lab methods like DEXA, so it is most useful for tracking changes over time.
Results are estimates for general information only and are not medical advice. Talk to a doctor or registered dietitian before making major changes.
Formula
All measurements in centimeters, using base-10 logarithms:
Men: %BF = 495 ÷ (1.0324 − 0.19077·log(waist − neck) + 0.15456·log(height)) − 450
Women: %BF = 495 ÷ (1.29579 − 0.35004·log(waist + hip − neck) + 0.22100·log(height)) − 450
Fat mass = weight × %BF; lean mass = weight − fat mass. Categories follow the American Council on Exercise ranges (men: athletes 6–13%, fitness 14–17%, average 18–24%; women: athletes 14–20%, fitness 21–24%, average 25–31%).
Example calculation
Using the default values:
- Sex = Male
- Units = US (ft, in, lb)
- Height – feet = 5 ft
- Height – inches = 10 in
- Weight (for fat mass) = 170 lb
- Neck circumference = 15 in
- Waist circumference = 34 in
the calculator returns:
- Body fat: 17.4%
- Category: Fitness
- Fat mass: 29.6 lb
- Lean mass: 140.4 lb
Frequently asked questions
What is a healthy body fat percentage?
Roughly 14–24% for men and 21–31% for women falls in the fitness-to-average range for adults. Healthy ranges rise slightly with age.
How accurate is the Navy body fat method?
Compared with DEXA scans it usually lands within a few percentage points, but it can be less accurate for people with unusual fat distribution or very muscular necks.
Where do I measure my waist?
Men measure horizontally at the level of the navel. Women measure at the narrowest part of the waist, usually just above the navel. Relax and breathe out normally before reading the tape.
Last updated: · Category: Health & Fitness calculators