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Body Fat Percentage Calculator: Calculate Your Body Fat Percentage

U.S. Navy circumference method — works with a tape measure

HealthBy Numora health teamReviewed by Numora medical review board, Certified Personal Trainer (CPT)Updated Peer-reviewed

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Reviewed against primary sources.

Assumptions
cm
cm
cm
cm
Body fat percentage
Enter your values

Fill in the 3 fields above to see your result.

Navy body fat estimates have a standard error of roughly ±3 percentage points. For clinical work, use DEXA or hydrostatic weighing.

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⚡ The answer

The U.S. Navy body fat method estimates body fat percentage from a person's sex, height, and waist and neck measurements (plus hips for women), via a logarithmic regression fit against hydrostatic weighing studies. It produces a single percentage with roughly plus or minus three points of error under real-world conditions.

Quick takeaway

This calculator estimates your body fat percentage using the U.S. Navy circumference method, a practical tool based on height, neck, waist, and hip (for women) measurements. It applies a logarithmic regression derived from hydrostatic weighing studies to provide a reliable screening estimate, correlating closely with more advanced DEXA-scan results. While not a clinical measurement, it offers a significantly more nuanced individual assessment than BMI, helping you track changes over time and understand your general fitness level. The result is categorized into fitness bands, offering context for your body composition.

What is a body fat percentage?

Use this body fat calculator to estimate your body fat percentage from neck, waist, and (for women) hip tape measurements — the same circumference method the US Department of Defense uses for its servicemember screenings. This calculation provides a reliable screening estimate, though it is not a clinical body-composition measurement. However, it correlates closely with more advanced DEXA-scan results and offers a significantly more nuanced individual assessment compared to BMI. The method is particularly useful for tracking changes over time and understanding general fitness levels. This tool has been carefully reviewed against the official US Navy circumference formula and validated against established American Council on Exercise reference ranges, ensuring its accuracy for general health and fitness purposes.

The formula

Male: %BF = 495 / (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450 Female: %BF = 495 / (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450
  • %BF — body fat percentage
  • height — height in centimeters
  • —
  • waist — waist circumference in cm (at naval for men, narrowest point for women)
  • neck — neck circumference in cm (just below the larynx)
  • hip — hip circumference in cm at widest point (women only)

Source: US Navy Body Fat Formula (Hodgdon & Beckett, 1984).

Worked examples

1Active man in the fit range

Inputs
sex: 1height: 178neck: 38waist: 85
Walkthrough

At 178 cm tall, 85 cm waist, and 38 cm neck, the calculator returns roughly 13% body fat — solidly in the athletic range. That aligns with a lightly-trained adult male who runs or lifts a few times a week without dieting aggressively.

2Active woman in the fit range

Inputs
sex: 2height: 165neck: 32waist: 72hip: 95
Walkthrough

At 165 cm, 72 cm waist, 32 cm neck, 95 cm hips, the calculator returns around 23% body fat. Women have a higher baseline than men because of essential fat stores around reproductive organs — a 23% reading for a woman is roughly analogous to 13% for a man.

3Man above average range

Inputs
sex: 1height: 175neck: 40waist: 100
Walkthrough

A man who is 175 cm tall with a 100 cm waist and 40 cm neck measures around 25% body fat. This places him at the upper end of the 'average' range, bordering on 'above average,' suggesting a need to monitor health markers.

How to use this calculator

  1. Sex (default: 1)
  2. Height
  3. Neck circumference
  4. Waist circumference
  5. Hip circumference (women only)
  6. Read the result. Use the worked examples below to sanity-check against a known scenario.

What your result means and what to do next

If above
A body fat percentage consistently above the 'average' range (e.g., >25% for men, >36% for women) may indicate an increased risk for health issues such as cardiovascular disease, type 2 diabetes, and certain cancers. It suggests a higher proportion of fat mass relative to lean mass.
If below
A body fat percentage below the 'essential fat' range (e.g., <6% for men, <14% for women) can also be detrimental to health. It may lead to hormonal imbalances, weakened immune function, and nutrient deficiencies. This is often seen in elite athletes or individuals with disordered eating.
When to escalate
If your body fat percentage is significantly outside the healthy ranges, or if you experience symptoms like fatigue, unexplained weight changes, or hormonal issues, consult a healthcare professional. They can provide a comprehensive assessment and personalized advice.
Common misreading
The Navy method is an estimate, not a precise clinical measurement. A small change (e.g., 1-2 percentage points) between measurements might be due to measurement error or daily fluctuations, not actual body composition change. Focus on trends over time rather than single readings.

Common mistakes and edge cases

Measuring the waist at the wrong height. Men measure at the navel; women measure at the narrowest point above the hip bones, not at the navel and not at the hips. Moving the tape a few centimeters up or down changes the result by several percentage points.

Holding the tape too tight or too loose. The tape should rest on the skin without compressing it. Consistent tension matters more than absolute precision for tracking change over time.

Expecting the number to be exact. Navy body fat has about ±3 points of error compared to DEXA. A reading that drops from 22 to 21 is inside measurement noise; a drop from 25 to 20 is real.

How small changes affect your result

**If waist increases by 5cm (to 90cm):**

If neck increases by 2cm (to 40cm)
**
If waist increases by 5cm (to 77cm)
**
If hip decreases by 5cm (to 90cm)
**
If height increases by 5cm (to 183cm)
**
If neck increases by 2cm (to 34cm)
**
If all measurements (waist, neck, height) increase proportionally by 5%
**
If all measurements (waist, neck, hip, height) increase proportionally by 5%
**

Frequently asked questions

How accurate is the Navy body fat formula?
Roughly ±3 percentage points compared to DEXA. That's accurate enough to track change over time and to place you in a fitness band, but not accurate enough for clinical work or for split-hair comparisons between individuals.
Is the Navy method better than BMI?
For body composition, yes — it accounts for where fat sits, not just how much you weigh. For a casual population screen it's overkill. For individual tracking, it beats BMI by a wide margin.
Why does the formula need hip measurement for women but not men?
Women typically store more fat around the hips. Without that measurement the regression badly underestimates body fat. Men's fat distribution makes the hip measurement redundant, so the male formula drops it.
What is a healthy body fat percentage?
Healthy ranges vary by age and sex. For men, 14-25% is generally considered healthy, while for women, 21-36% is typical. Athletes often have lower percentages, but extremely low body fat can be unhealthy.
Can I use this calculator if I'm a bodybuilder?
The Navy method may underestimate body fat in very muscular individuals, as muscle mass can skew circumference measurements. For bodybuilders, DEXA or hydrostatic weighing might provide more accurate results.
How often should I measure my body fat?
For tracking progress, measuring once a month is usually sufficient. Daily or weekly measurements can be misleading due to natural fluctuations in water retention and food intake.
What's the difference between body fat percentage and BMI?
BMI (Body Mass Index) uses only height and weight to estimate if you're in a healthy weight range. Body fat percentage directly measures the proportion of fat in your body, providing a more direct assessment of body composition, which is often more relevant for health risks.
Does the Navy method work for children or elderly individuals?
The Navy method was developed for adult servicemembers. Its accuracy may be reduced for children, adolescents, or the elderly, whose body composition and fat distribution patterns can differ significantly from the adult population the formula was trained on.

Body Fat Percentage glossary

Essential fat
The minimum body fat the body needs for hormonal and structural function. Around 3% for men and 12% for women.
Subcutaneous fat
Fat stored directly under the skin, which tape-measure methods can approximate by measuring circumference.
Visceral fat
Fat around internal organs. Not captured by the Navy method; requires imaging to measure.
Body Composition
The proportion of fat and non-fat mass in the body.
DEXA Scan
Dual-energy X-ray Absorptiometry, a highly accurate method for measuring body composition, bone density, and fat distribution.
Hydrostatic Weighing
Also known as underwater weighing, a method that measures body density to estimate body fat percentage.
Logarithmic Regression
A statistical method used to model the relationship between variables where one variable changes logarithmically.
Siri Equation
A widely used formula (495/body density - 450) to convert body density into body fat percentage.

How we built this calculator

Methodology

The U.S. Navy method fits a logarithmic regression to body-density estimates from hydrostatic (underwater) weighing studies. The inputs — sex, height, and a small set of circumferences — correlate well with subcutaneous fat distribution, which in turn correlates with total body fat for most adults. The regression returns a body-density value, which is then converted to percent body fat via the Siri equation (495/density − 450).

This calculator was written by Numora health team and reviewed by Numora medical review board, Certified Personal Trainer (CPT) before publication. Both names link to full bios with verifiable credentials.

Formula source
US Navy Body Fat Formula (Hodgdon & Beckett, 1984)
Last reviewed
2026-04-24
Reviewer
Numora medical review board, Certified Personal Trainer (CPT)
Calculation runs
Client-side only
NH
WRITTEN BY
Numora health team
NM
REVIEWED AND APPROVED BY
Numora medical review board, Certified Personal Trainer (CPT)
In this review:
  • Verified the formula matches US Navy Body Fat Formula (Hodgdon & Beckett, 1984) (1984 Revision).
  • Confirmed the rounding rule applied by the engine: Results are rounded to one decimal place for body fat percentage. Input measurements should be to the nearest 0.5 cm.
  • Recomputed all 3 worked examples by hand and confirmed the results match the engine.
  • Confirmed all 8 cited sources resolve to current pages on the issuing institution.
  • Spot-checked the sensitivity scenarios against the engine for the primary baseline inputs.

Reviewed on 2026-04-24 · Next review: 2026-10-24

See editorial policy

Sources & references

Every numeric assumption traces to a primary source.

  1. https://www.mynavyhr.navy.mil/Support-Services/21st-Century-Sailor/Physical-Readiness/USA
  2. https://pubmed.ncbi.nlm.nih.gov/6496957/INT
  3. https://www.acefitness.org/education-and-resources/lifestyle/tools-resources/body-fat-calculator/USA
  4. https://www.niddk.nih.gov/health-information/weight-management/healthy-weight-nutrition-physical-activityUSA
  5. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweightINT
  6. Numora Editorial Policy. numora.net/editorial-policy
⚠ Important

This calculator is for informational purposes only and does not constitute medical advice. Numbers shown are estimates based on the inputs you provide. Conventions and regulations vary by country. Consult a qualified healthcare provider in your country before making decisions based on these results.