Estimate body fat percentage with the US Navy circumference formula or a BMI-based method—metric or imperial, instant results, nothing uploaded.
Runs in your browser · No data stored · No signup
A body fat calculator estimates what percent of your weight is fat versus lean tissue. This tool supports the US Navy circumference method (waist, neck, hip) and a BMI-plus-age formula—calculated locally in your browser.
US Navy body fat estimates have ±3–4% accuracy versus DEXA scans—results are for fitness tracking only, not a medical measurement. Consult a physician or certified trainer for clinical body composition assessment.
Body fat percentage describes how much of your total weight is adipose (fat) tissue versus lean mass (muscle, bone, organs, water). Unlike BMI alone, it speaks to composition—not just scale weight.
The US Navy method uses height and girth measurements at standardized sites (waist at navel, neck below the larynx, hip for women). The BMI method uses height, weight, age, and sex when you do not have a tape measure handy.
Neither method is DEXA-accurate for every individual, but consistent monthly checks reveal real trends. Pair results with a lean body mass calculator when you need muscle versus fat planning numbers.
US Navy for tape measurements; BMI method when you only know height and weight. Runs locally—nothing uploaded.
Choose US Navy if you can measure waist and neck (and hip for women). Choose BMI when you only have height, weight, and age.
Enter height and circumferences in cm/kg or in/lb—the calculator converts internally for the formulas.
Waist at navel after a normal exhale; neck just below the larynx; hip at widest point for women. Use a soft tape, not metal.
Compare the percentage to typical athletic, fitness, and average ranges for your sex—use as screening, not diagnosis.
Use lean body mass or calorie calculators to turn body fat % into training and nutrition targets.
Common real-world scenarios where this tool saves time.
Monthly body fat % to see whether weight change is mostly fat or lean tissue.
Estimate US Navy-style body fat from standard circumference measurements.
Affordable tracking when lab scans are unavailable—focus on trends, not one number.
Feed body fat % into LBM and protein or calorie tools for sharper targets.
Step-by-step chains that connect related tools for common tasks.
Estimate fat, then plan LBM, protein, and energy needs.
| Factor | US Navy (circumference) | BMI + age formula |
|---|---|---|
| Inputs | Height, waist, neck, hip (women) | Height, weight, age, sex |
| Best for | Home tracking with a soft tape | Quick estimate without girth measurements |
| Muscular athletes | Often more realistic than BMI alone | May overestimate fat if BMI is high from muscle |
| Consistency | Sensitive to measure site and tape technique | Sensitive to scale weight and age entry |
| Related tool | Use this tool when | Use related tool when |
|---|---|---|
| Lean Body Mass Calculator | You have a body fat % and want exact lean mass, BMR, and target weight at a goal BF%. | You only need fat percentage first—start here, then convert LBM downstream. |
| BMI Calculator | You want composition context beyond height and weight screening. | You only need a quick BMI category without circumference measurements. |
US Navy protocol uses navel level after a normal exhale—not the smallest waist curve.
Stand relaxed, exhale normally, keep tape snug without compressing skin.
High muscle can inflate BMI; prefer Navy measurements when possible.
Likely cause: Waist must be larger than neck; missing hip for women; invalid numbers.
Fix: Double-check units, ensure female hip is entered, and remeasure circumferences.
Likely cause: Hydration, meals, or inconsistent tape placement.
Fix: Measure monthly, same time of day, same technique.
Advertisement
The US Navy method has an error margin of roughly ±3–4 percentage points versus reference methods like DEXA for many adults. Accuracy drops with inconsistent tape placement. The real value is tracking change over time with the same technique.
It uses logarithms of waist, neck, hip (women), and height in centimeters. Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Women add hip into the log term. This calculator applies those equations automatically.
At navel level after a normal exhale, feet together, soft non-stretch tape snug to skin. Measure twice and average. Avoid post-meal bloating or post-workout pumps for consistency.
Just below the larynx (Adam's apple), tape perpendicular to the neck axis, head level and relaxed. Average two readings.
Body fat reflects composition; BMI only uses height and weight. Muscular people can have high BMI but low fat—body fat % often tells a clearer story for fitness goals.
Guidelines vary by sex. Men: athletic ~6–13%, fitness ~14–17%, average ~18–24%. Women: athletic ~14–20%, fitness ~21–24%, average ~25–31%. Genetics and age shift what is realistic.
Women carry more essential fat for hormonal and reproductive function—typically 8–13% more than men at comparable leanness.
Waist, neck, hip, height, and weight values are processed locally in your browser—they are not uploaded for body-fat estimates.
US Navy estimates often fall within ±3–4 percentage points of DEXA for many adults; consistency of measurement technique matters more than a single reading.
Fitness screening estimate only—not medical advice. DEXA, Bod Pod, or clinical assessment is more accurate for individual diagnosis—consult a healthcare provider for health decisions.
Part of Calculator Tools
More free tools for the same workflow.
Advertisement
Reviewed by EverydayTools Editorial Team on 2026-06-02.
Keys: 1 US Navy · 2 BMI method. Waist at navel; neck below Adam's apple.
Estimated body fat
16.9%
Fitness range (men)Method: US Navy circumference formula · BMI 26.1
Estimates are for fitness planning—not medical diagnosis. Measure monthly under the same conditions for meaningful trends.