Free Body Fat Calculator
Calculate your body fat percentage using the Navy method or BMI formula. Find your lean mass, fat mass, and ideal body fat range for your goals.
What Is Body Fat Percentage?
Body fat percentage is the proportion of your total body weight that consists of fat tissue. It's expressed as a percentage:
Body Fat % = (Fat Mass ÷ Total Body Weight) × 100 For example, if you weigh 180 lbs and have 36 lbs of fat, your body fat percentage is 20%.
Unlike BMI (which only considers height and weight), body fat percentage distinguishes between fat mass and lean mass (muscle, bones, organs, water). This makes it a much better indicator of body composition and health.
Healthy Body Fat Ranges
Ideal body fat varies by gender and goals. Here are the generally accepted ranges:
Men's Body Fat Ranges
| Category | Body Fat % | Description |
|---|---|---|
| Essential Fat | 2-5% | Minimum for survival; dangerous to maintain |
| Athletes | 6-13% | Competition-ready; hard to maintain year-round |
| Fitness | 14-17% | Visible muscle definition; sustainable for most |
| Average | 18-24% | Healthy; typical for active adults |
| Obese | 25%+ | Increased health risks |
Women's Body Fat Ranges
| Category | Body Fat % | Description |
|---|---|---|
| Essential Fat | 10-13% | Minimum for survival; can affect hormones |
| Athletes | 14-20% | Competition-ready; may affect menstrual cycle |
| Fitness | 21-24% | Toned appearance; sustainable for most |
| Average | 25-31% | Healthy; typical for active adults |
| Obese | 32%+ | Increased health risks |
How to Measure for the Navy Method
The Navy method requires specific body circumference measurements. Here's how to take them accurately:
📏 Neck
- Measure just below the larynx (Adam's apple)
- Tape should slope slightly downward at the front
- Pull snug but don't compress the skin
- Take measurement while looking straight ahead
📏 Waist (Men)
- Measure at navel (belly button) level
- Stand relaxed — don't suck in your stomach
- Keep tape horizontal all around
- Measure at the end of a normal exhale
📏 Waist (Women)
- Measure at the narrowest point of your torso
- This is usually between the ribs and hip bone
- If you don't have a natural waist, use navel level
- Stand relaxed, tape horizontal
📏 Hips (Women Only)
- Measure at the widest point of your buttocks
- Keep tape horizontal
- Stand with feet together
- View from the side to ensure the tape is level
Measurement Tips
- Use a flexible tape — Not a metal retractable tape measure
- Measure on bare skin — Or over thin, non-compressing clothing
- Be consistent — Same time of day, same conditions
- Take 3 measurements — Use the average for best accuracy
- Don't pull too tight — The tape should touch skin but not compress it
The Navy Method Explained
The U.S. Navy developed this formula to assess body composition for service members. It uses height and circumference measurements to estimate body fat percentage.
Navy Method Formula (Men)
BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 Navy Method Formula (Women)
BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 All measurements in inches or cm (formula adjusts internally)
Accuracy
The Navy method is typically accurate within ±3-4% when measurements are taken correctly. It's more accurate than BMI-based estimates but less precise than:
- DEXA scan — ±1-2% accuracy (gold standard)
- Hydrostatic weighing — ±1.5-2% accuracy
- Bod Pod — ±2-3% accuracy
- Quality calipers (7-site) — ±3% accuracy
The Navy method can overestimate body fat in very muscular individuals and underestimate in people with narrow waists but high visceral fat.
The BMI Method Explained
The BMI method estimates body fat using only height, weight, age, and gender. It's convenient but less accurate than the Navy method.
BMI-Based Body Fat Estimation
Adult BF% = (1.20 × BMI) + (0.23 × age) − (10.8 × gender) − 5.4 Where gender = 1 for males, 0 for females
Limitations: BMI doesn't distinguish between muscle and fat. A muscular person can have a "high" BMI but low body fat, while someone with little muscle might have "normal" BMI but high body fat (skinny-fat).
Understanding Lean Mass vs Fat Mass
Your body weight consists of two components:
💪 Lean Mass (FFM)
Everything that isn't fat:
- Skeletal muscle
- Bones
- Organs
- Water
- Connective tissue
Goal: Preserve and build lean mass for metabolism and health.
🔥 Fat Mass (FM)
All fat tissue, including:
- Essential fat (vital for health)
- Storage fat (energy reserve)
- Subcutaneous fat (under skin)
- Visceral fat (around organs)
Goal: Reduce excess storage fat while maintaining essential fat.
Why Lean Mass Matters
- Higher metabolism — Muscle burns more calories at rest than fat
- Better body composition — Same weight looks different with more muscle
- Functional strength — Everyday activities become easier
- Bone health — Resistance training increases bone density
- Metabolic health — Muscle helps regulate blood sugar
Body Fat Goals by Objective
🏆 Visible Abs
Men: 10-14%
Women: 16-19%
Abs start becoming visible. Going lower requires strict diet and may not be sustainable year-round.
💪 Athletic Look
Men: 12-17%
Women: 18-24%
Toned, muscular appearance without extreme leanness. Sustainable for most active people.
❤️ Health Optimization
Men: 15-20%
Women: 20-25%
Reduced disease risk without obsessive dieting. Good balance of health and lifestyle.
🏃 Endurance Sports
Men: 8-12%
Women: 15-20%
Lower fat improves power-to-weight ratio for running, cycling. Must balance with energy needs.
How to Improve Body Composition
The goal isn't just to lose weight — it's to lose fat while preserving (or building) muscle. Here's how:
1. Moderate Calorie Deficit
Aim for 15-25% below your TDEE. Larger deficits lead to more muscle loss. Use our calorie deficit calculator to find your target.
2. High Protein Intake
Consume 0.8-1.2g protein per pound of body weight — the single most important factor for preserving muscle during fat loss. Calculate your protein needs →
3. Resistance Training
Lift weights 3-4x per week. Without resistance training, up to 25% of weight lost can be muscle instead of fat. Focus on compound movements: squats, deadlifts, presses, rows.
4. Adequate Sleep
Poor sleep increases cortisol and shifts weight loss toward muscle instead of fat. Aim for 7-9 hours per night.
5. Patience
Sustainable fat loss is 0.5-1% of body weight per week. At 180 lbs, that's about 1-2 lbs per week. Going faster often means losing muscle.
Frequently Asked Questions
Everything you need to know about body fat percentage
What is a healthy body fat percentage?
For men, 10-20% is considered healthy/fit, with athletes often at 6-13%. For women, 18-28% is healthy/fit, with athletes at 14-20%. Essential fat (minimum for health) is 2-5% for men and 10-13% for women. These ranges vary by age.
How accurate is the Navy body fat method?
The Navy method is typically accurate within ±3-4% for most people. It's more accurate than BMI-based estimates but less precise than DEXA scans or hydrostatic weighing. For tracking trends over time, it's a reliable and free method.
How do I measure my waist for body fat calculation?
Measure your waist at the narrowest point, usually at or just above the navel. Stand relaxed, don't suck in your stomach. For the Navy method, measure horizontally around your natural waist. For women, also measure hips at the widest point.
What's the difference between body fat and BMI?
BMI is a simple ratio of weight to height that doesn't distinguish between muscle and fat. Body fat percentage specifically measures the proportion of your weight that is fat tissue. Someone muscular can have a high BMI but low body fat.
What body fat percentage do I need for visible abs?
For men, abs typically become visible around 10-14% body fat, with clear definition at 8-10%. For women, abs show around 16-19% body fat. However, genetics play a role — some people see abs at higher percentages.
How much lean mass should I have?
Lean mass includes muscle, bones, organs, and water — everything except fat. There's no universal 'ideal' lean mass, but preserving and building lean mass is important for metabolism and health. Focus on maintaining muscle through strength training while losing fat.
Can I lose fat and gain muscle at the same time?
Yes, this is called body recomposition. It works best for beginners, those returning after a break, or people with higher body fat. Eat at maintenance calories or a small deficit, keep protein high (0.8-1g per pound), and lift weights consistently.
How often should I measure body fat?
Measure every 2-4 weeks under consistent conditions (same time of day, same hydration level). Body fat changes slowly, so more frequent measurements add noise without useful information. Focus on trends over months.
Why does my body fat percentage fluctuate?
Fluctuations are normal and can be caused by hydration levels, time of day, recent meals, and measurement technique. For the Navy method, small changes in tape tightness can affect results. Always measure consistently and track averages.
What's the most accurate way to measure body fat?
DEXA scans are considered the gold standard (±1-2% accuracy), followed by hydrostatic weighing and Bod Pod. For home use, the Navy method and quality calipers are the most practical options (±3-4%). Bioelectrical impedance scales are convenient but less reliable.
References
- Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men from body circumferences and height. Naval Health Research Center. 1984. Report
- Hodgdon JA, Friedl K. Development of the DoD body composition estimation equations. Naval Health Research Center. 1999.
- Deurenberg P, Weststrate JA, Seidell JC. Body mass index as a measure of body fatness: age- and sex-specific prediction formulas. Br J Nutr. 1991;65(2):105-114. PubMed
- Jackson AS, Pollock ML. Generalized equations for predicting body density of men. Br J Nutr. 1978;40(3):497-504. PubMed