Body Fat Percentage Calculator
Estimate your body fat percentage using the accurate US Navy method or the simpler BMI method. See your fat mass, lean mass, and ACE fitness classification.
How to use Body Fat Percentage Calculator
This body fat percentage calculator uses either the US Navy circumference method or the BMI-based estimation to estimate the percentage of your body composed of fat. The US Navy method — measuring waist, neck and (for women) hip circumferences — is widely used and requires no special equipment. Once you have your body-fat percentage, this tool also shows your fat mass versus lean mass split, and classifies you using American Council on Exercise (ACE) categories.
- Choose your gender and preferred method (US Navy or BMI-based).
- Select imperial (inches) or metric (cm) units.
- For US Navy: enter height, waist, neck and (females) hip measurements.
- For BMI method: enter height and weight.
- Optionally enter body weight to see fat mass and lean mass in absolute terms.
Your data never leaves your device — 100% private processing.
US Navy formula explained
The US Navy method uses logarithms of circumference measurements to estimate body density and thus body fat. For men: 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. For women the hip measurement is added. Measure the waist at the narrowest point (navel level for men) and the neck just below the Adam's apple. Accuracy is within ±3–4% for most people, improving with multiple measurements.
ACE body fat categories
The American Council on Exercise defines five categories for men: Essential Fat (2–5%), Athletes (6–13%), Fitness (14–17%), Average (18–24%) and Obese (≥25%). Women carry more essential fat for hormonal function: Essential (10–13%), Athletes (14–20%), Fitness (21–24%), Average (25–31%) and Obese (≥32%). These thresholds help contextualise a number that is hard to interpret in isolation.
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | ≥25% | ≥32% |
Limitations and best practices
All estimation methods carry error. DEXA scanning (±1–2%) and hydrostatic weighing are more accurate but require clinical equipment. Circumference methods can vary by 3–5% depending on measurement consistency. Take measurements first thing in the morning before eating, and use the same tape tension each time. Track trends over 4–8 weeks rather than single readings for a meaningful picture of progress.
Glossary
- Essential Fat
- The minimum fat required for physiological function; below this causes serious health risks.
- Lean Mass
- Everything in the body that is not fat: muscle, bone, organs and water.
- DEXA
- Dual-energy X-ray absorptiometry — gold-standard body composition scan.
- Circumference method
- Body fat estimation using tape measurements of specific body sites.
Related reading
Frequently Asked Questions
Get weekly tool tips & updates
New tools, power-user tips, and productivity hacks — delivered free every Friday.
No spam, ever. Unsubscribe with one click.
Why use Body Fat Percentage Calculator?
- Based on widely-accepted clinical and scientific formulas
- No personal data stored — all calculations run locally
- Supports both metric and imperial units
- Results include actionable recommendations
Common use cases
- Calculate BMI before a doctor's appointment
- Estimate daily calorie needs for a weight loss goal
- Track ideal body weight range for a fitness plan
- Calculate pregnancy due date
- Find out your recommended water intake based on body weight
Related Health & Fitness
BMI Calculator
Calculate your Body Mass Index (BMI) instantly. Supports metric (kg/cm) and imperial (lbs/ft+in) units. Free online BMI calculator.
BMR Calculator
Calculate your Basal Metabolic Rate (BMR) using Mifflin-St Jeor, Harris-Benedict, or Katch-McArdle formula. Free online BMR calculator.
TDEE Calculator
Calculate your Total Daily Energy Expenditure (TDEE) and get personalized calorie and macro targets for weight loss, maintenance, or muscle gain.
Ideal Weight Calculator
Calculate your ideal body weight using 4 proven formulas: Robinson, Miller, Devine, and Hamwi. Find the healthy weight range for your height.
Macro Calculator
Calculate your daily macronutrients (protein, carbs, fat) for your fitness goals. Free macro calculator for weight loss, muscle gain, keto, and more.
Pregnancy Due Date Calculator
Calculate your estimated due date (EDD) from last period, conception date, or IVF transfer. Shows gestational age, trimesters, and key milestones.
Explore all Health & Fitness.