Body Fat Percentage Calculator
Estimate your body fat percentage using the US Navy tape-measure method (neck, waist, and height) or the BMI-based Deurenberg formula — choose your sex, enter your measurements, and instantly see your body fat percentage, fat mass, lean mass, and category (Essential, Athletic, Fitness, Average, or Obese) on a colour-coded scale. Supports metric and imperial units. Free, private, and no signup required.
Choose the US Navy method (neck, waist, and height measurements) or the BMI method (weight, height, and age) to estimate your body fat percentage. See your fat mass, lean mass, and body fat category. All calculations run locally in your browser — no data is sent to any server.
Measure without shoes
At navel level
Below larynx, sloping downward
Used to compute fat/lean mass
Important Notes:
- The US Navy method is an estimate — accuracy is ±3–4% compared to DEXA scans.
- The BMI method is less accurate for athletes and muscular individuals.
- Measure circumferences at the same time of day for consistent results.
- Consult a healthcare professional for a clinical body composition assessment.
Why Use Our Body Fat Percentage Calculator?
Two Accurate Calculation Methods
Our body fat calculator supports the US Navy method (neck, waist, and height — the most accurate tape-measure formula at ±3–4%) and the BMI-based Deurenberg formula (weight, height, and age). Both methods use sex-specific formulas for male and female, and both support metric and imperial units.
Full Breakdown with Visual Scale & Categories
See your body fat percentage on a colour-coded scale, your fat mass and lean mass in kilograms, a body composition bar, and a category reference table showing Essential, Athletic, Fitness, Average, and Obese ranges for your sex — all in one view.
Completely Private & Secure
All body fat calculations happen locally in your browser. Your measurements, weight, and health data are never sent to any server — 100% private when you use our body fat percentage calculator online.
No Installation Required
Use our free body fat calculator directly in your browser — no downloads, no plugins, no account needed. Works on any device with metric (cm, kg) and imperial (inches, lbs) unit support.
Common Use Cases for Body Fat Percentage Calculator
Fitness & Strength Training Progress
Gym-goers and strength athletes use the body fat calculator to track body composition changes over time — not just weight. Monitoring body fat percentage alongside lean mass reveals whether a training programme is building muscle, losing fat, or both.
Endurance Athletes & Runners
Runners and cyclists use the body fat calculator to optimise their power-to-weight ratio. Knowing fat mass versus lean mass helps athletes determine whether weight loss would improve performance without sacrificing muscle.
Weight Loss & Body Recomposition
People on a weight loss journey use the body fat calculator to ensure they are losing fat rather than muscle. Tracking body fat percentage alongside scale weight gives a more complete picture of progress than weight alone.
Bodybuilding & Competition Prep
Competitive bodybuilders use the body fat calculator to monitor their cut phase and estimate when they will reach stage-ready body fat levels. The Athletic and Essential Fat categories provide clear targets for competition preparation.
Health Risk Assessment
Healthcare professionals and individuals use the body fat calculator to assess metabolic health risk. High body fat percentage — particularly in the Obese category — is associated with increased risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome.
Personal Health Monitoring
Health-conscious individuals use the body fat calculator as part of their regular health check-in alongside BMI, blood pressure, and resting heart rate. The body fat percentage calculator provides a more accurate health picture than BMI alone for muscular individuals.
Understanding Body Fat Percentage
What is Body Fat Percentage?
Body fat percentage is the proportion of your total body weight that is made up of fat tissue. It is a more accurate indicator of health and fitness than body weight or BMI alone because it distinguishes between fat mass (adipose tissue) and lean mass (muscle, bone, organs, and water). Essential fat — the minimum required for physiological function — is 2–5% for men and 10–13% for women. Our browser-based body fat percentage calculator supports two methods: the US Navy tape-measure method and the BMI-based Deurenberg formula.
How Our Body Fat Calculator Works
- Choose a Method: Select the US Navy method for a more accurate tape-measure estimate, or the BMI method for a quick estimate using weight, height, and age. Choose your sex and unit system (metric or imperial).
- Enter Your Measurements: For the Navy method, measure your height, waist (at navel for men, narrowest point for women), neck (below the larynx), and hip (widest point, women only). For the BMI method, enter weight, height, and age.
- Instant Browser-Based Calculation: Click Calculate Body Fat. The body fat calculator applies the correct sex-specific formula entirely in your browser — your health data is never sent to any server.
The Two Formulas Explained
- US Navy Method (Male): %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. All measurements in cm. Accuracy: ±3–4% compared to DEXA scan.
- US Navy Method (Female): %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. Hip measurement is required for the female formula.
- BMI Method (Deurenberg Formula): %BF = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4, where sex = 1 for male and 0 for female. Less accurate for athletes and muscular individuals.
- Fat Mass & Lean Mass: Fat Mass = Body Weight × (BF% ÷ 100). Lean Mass = Body Weight − Fat Mass. These are computed from your weight input alongside the body fat percentage.
Important Limitations
The body fat percentage calculator provides an estimate, not a clinical measurement. The most accurate methods — DEXA scan, hydrostatic weighing, and Bod Pod — require specialist equipment. The Navy method has an accuracy of ±3–4% and may underestimate body fat in very muscular individuals. The BMI method is less accurate for athletes, elderly individuals, and those with unusual muscle-to-fat ratios. Always consult a healthcare professional for a clinical body composition assessment before making significant health decisions.
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Frequently Asked Questions About Body Fat Percentage Calculator
A body fat percentage calculator estimates the proportion of your body weight that is fat tissue. Our body fat calculator supports two methods — the US Navy tape-measure method and the BMI-based Deurenberg formula — with sex-specific formulas, a visual scale, fat mass and lean mass breakdown, and body fat category classification. Everything runs locally in your browser with no signup required.
The US Navy method is generally more accurate for most people, with an accuracy of ±3–4% compared to DEXA scans. The BMI method is a quick estimate that works reasonably well for average-build individuals but is less accurate for athletes, muscular individuals, and the elderly. For the most accurate results, use the Navy method with careful measurements.
For the waist: men measure at the navel level; women measure at the narrowest point of the torso. For the neck: measure just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. For the hip (women only): measure at the widest point of the hips and buttocks. Take measurements in the morning before eating, and measure twice for accuracy.
For men, the Fitness category (14–17%) is considered healthy and fit. For women, the Fitness category (21–24%) is healthy. The Athletic category (6–13% for men, 14–20% for women) is typical of competitive athletes. The Average category is normal for the general population but carries some health risk at the higher end.
Essential fat is the minimum body fat required for basic physiological functions — hormone production, organ protection, and nerve function. For men, essential fat is 2–5%; for women, it is 10–13% (higher due to sex-specific fat in breasts and reproductive organs). Falling below essential fat levels is dangerous and associated with serious health complications.
BMI only measures weight relative to height and cannot distinguish between fat mass and muscle mass. A muscular athlete may have a high BMI but low body fat, while a sedentary person may have a normal BMI but high body fat. Body fat percentage directly measures the fat-to-lean ratio, making it a more accurate indicator of health and fitness.
For tracking fitness progress, measuring every 4–6 weeks is sufficient. Daily measurements are not recommended because body fat estimates can vary by 1–2% based on hydration, time of day, and measurement technique. Always measure under the same conditions — same time of day, same hydration state — for consistent comparisons.
Absolutely. All body fat calculations run entirely in your browser. Your measurements, weight, age, and health data are never sent to any server, stored in a database, or tracked. Everything stays completely private on your device.
Yes. The body fat calculator is 100% free with no signup required, no premium tier, no usage quotas, and no ads blocking the interface. Calculate your body fat percentage as many times as you need, directly in your browser.