Free Body Fat Calculator
Estimate body fat percent from body measurements (US Navy method).
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Inputs
Result
Body fat
16.4%
Fit
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Short answer
The US Navy method estimates body fat from log-transformed circumferences at the waist, neck (and hip for women) scaled by height.
What is the Body Fat Calculator?
Body fat is the proportion of body mass that is adipose tissue. The Navy method uses circumferences as a low-cost proxy.
How does the Body Fat Calculator work?
Measure height, waist (at navel), neck, and — for women — hip at widest. Apply the log-transform regression for the chosen sex.
Formula
Variables
waist / neck / hip / hCircumferences and height in cm
Explanation
Regression fit developed by Naval Health Research Center in the 1980s. Accurate within ±3–4% for most adults.
Examples
Example 1: 178 cm male, 85 cm waist, 38 cm neck
About 17% body fat, in the 'Fit' range.
Applications
- Military/service standards
- Fitness tracking without calipers
- Weight-loss goal setting
Advantages
- Requires only a tape measure
- Reasonable accuracy at population level
Limitations
- Less accurate for very lean or very heavy individuals
- Cannot see visceral vs subcutaneous fat
Common mistakes
- Measuring waist above the navel — always measure at navel level
Tips
- Use a flexible measuring tape; keep it snug but not compressing skin
Related concepts
The Body Fat Calculator sits inside the Health Calculators hub, in the body composition cluster. What body mass is made of and how it is distributed. Understanding the terms below makes the output easier to interpret and easier to compare against neighbouring measures.
Practical use cases and industry applications
Understanding Body Fat
Body fat is the proportion of body mass that is adipose tissue. The Navy method uses circumferences as a low-cost proxy. Within health calculators, body fat belongs to the body composition cluster, where it shares terminology and assumptions with closely related tools.
Learning how body fat is calculated
Regression fit developed by Naval Health Research Center in the 1980s. Accurate within ±3–4% for most adults. Working through the variables one at a time — waist / neck / hip / h — makes the result reproducible by hand and easier to sanity-check.
Using body fat to make a decision
Military/service standards Fitness tracking without calipers Weight-loss goal setting Because outputs depend on the assumptions you enter, run more than one scenario before committing to a figure.
How body fat compares with related measures
fat mass, lean mass, adiposity, percentile all describe adjacent aspects of body composition. Comparing this calculator's output against those measures — using the related tools listed on this page — prevents a single metric from being read in isolation.
Frequently asked questions
How accurate is it?
Compared to DEXA scans, the Navy method is typically within ±3.5%. DEXA and hydrostatic weighing are more accurate but cost significantly more.
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