Health & Fitness Hub

Body Fat
Calculator

Estimate your body fat percentage using the US Navy Method — the most accurate formula that doesn't require calipers or DEXA scans. Takes three simple tape measurements. Also shows a BMI-based estimate for comparison, fat mass, lean mass, and your fitness category.

Your Measurements

Height

Weight

Waist circumference

Measure at the narrowest point (for women) or at the navel (for men). Exhale normally before measuring — don't suck in.

Neck circumference

Measure just below your larynx (Adam's apple), keeping the tape horizontal. Stand upright and look straight ahead.

Age

yrs

US Navy Method

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Fitness Category

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body fat

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Fat Mass

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Lean Mass

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BMI-Est %

Body Fat Categories

Category	Men	Women	Your BF%

Step 2 of 5 ✓ — You know your body fat. Next: calculate your TDEE (Total Daily Energy Expenditure) to find your daily calorie target.

Calculate Your TDEE →

📏 How to Use This Calculator

Select your sex

Click Male or Female at the top. The Navy Method uses different formulas for men and women — women require a hip measurement that men don't. The category thresholds also differ because women naturally carry more essential fat than men (10–13% vs 2–5%). This is not a flaw — it's physiologically accurate.

Choose your units

Select Imperial (feet, inches, pounds) or Metric (centimeters, kilograms) using the toggle under the measurements header. The calculator converts between units automatically — you can switch at any time without re-entering your data.

Enter your measurements

You need height, weight, waist, and neck (women also need hip measurement). Take all measurements with a soft tape measure. Measure in the morning before eating if possible. See the Measurement Guide below for exact instructions on where to place the tape for each measurement to ensure accuracy.

Read your results

The gauge shows where you fall across five fitness categories from Essential Fat to Obese. Your fat mass and lean mass in pounds (or kg) are shown below. The BMI-based estimate is shown for comparison — it's less accurate but requires no measurements. Check the category table to see all thresholds and where you sit.

📐 Exact Measurement Guide — Where & How to Measure

⬆️ Waist (Men)

Measure at the level of your navel. Stand relaxed, exhale normally (don't suck in), and wrap the tape horizontally. The tape should be snug but not compressing the skin. Take 2–3 readings and use the average if they vary.

↔️ Waist (Women)

Measure at the narrowest point between your ribcage and navel — typically 1–2 inches above the navel. Look in a mirror to confirm the tape is horizontal all the way around. Exhale gently before reading.

🔵 Neck

Measure just below the larynx (the bump in the middle of your throat). Stand upright, look straight ahead — don't tilt your chin. The tape should slope slightly downward toward the front. Keep it snug but not tight. This is typically 14–18" for most adults.

🟣 Hips (Women only)

Measure at the widest part of the hips and buttocks. Stand with feet together, look in a mirror or have someone assist. The tape must be parallel to the floor — it's common for it to ride up in back, which underestimates the measurement. Take the largest reading.

Accuracy tips: Use a flexible tailor's tape measure, not a metal tape. Measure on bare skin or thin fabric. Take all measurements in the same session. Morning measurements (before eating) tend to be most consistent. Repeat the measurement weekly rather than daily — short-term fluctuations of 0.5–1% are normal from hydration alone. The Navy Method has an error margin of ±3–4% compared to DEXA scans.

Why body fat % is more useful than BMI

BMI (Body Mass Index) uses only height and weight — it can't distinguish between muscle and fat. A muscular athlete and an obese sedentary person can have identical BMIs. Body fat percentage directly measures what matters: how much of your body weight is fat tissue vs lean mass (muscle, bone, organs, water). A man at 15% body fat is lean regardless of BMI. A man at 30% body fat is obese regardless of BMI. For anyone who exercises regularly, body fat % is a far more meaningful metric.

How the US Navy Method works

The Navy Method was developed for the US military to assess fitness without calipers or body water testing. It uses circumference measurements as a proxy for body composition. The formula uses the natural logarithm of the difference between waist and neck measurements (and hip for women) relative to height. It's not perfectly accurate — margin of error is ±3–4% vs DEXA — but it's the most accurate method available without equipment. It's more reliable than BMI for most people.

What is a healthy body fat percentage?

For men, 6–17% is generally considered fit to athletic, 18–24% is acceptable, and 25%+ is overweight. For women, 14–24% is fit to athletic, 25–31% is acceptable, and 32%+ is overweight. These thresholds vary by age — older adults naturally carry more body fat and the health implications differ. Essential fat (the minimum needed for physiological function) is ~2–5% for men and ~10–13% for women. Going below these levels is dangerous.

Body fat vs BMI: when each is better

Use body fat % when: you exercise regularly, you're tracking body recomposition (losing fat while gaining muscle), you're an athlete, or you want a more clinically meaningful metric. Use BMI when: you have no way to take measurements, you're doing population-level screening, or you need a rough baseline. Most fitness professionals, personal trainers, and sports medicine doctors use body fat % as their primary metric and use BMI only as a secondary cross-check.

Frequently Asked Questions

How accurate is the Navy Method body fat calculator? ▾

The US Navy Method has an accuracy of approximately ±3–4% compared to DEXA (dual-energy X-ray absorptiometry) scans, which are considered the gold standard for body fat measurement. This means if your true body fat is 20%, this calculator might show 17–23%. It's significantly more accurate than BMI-based estimates, and better than most consumer bioelectrical impedance scales. For the most accurate results, take measurements consistently (same time of day, same hydration level) and track trends over time rather than fixating on a single reading.

Why does the calculator show a different number than my smart scale? ▾

Consumer bioelectrical impedance analysis (BIA) scales — including those from Fitbit, Garmin, and Withings — send a small electrical current through your body and estimate fat based on resistance. Their accuracy varies dramatically with hydration: being dehydrated can inflate the reading by 2–5%, and being well-hydrated can deflate it. The Navy Method tends to be more stable and consistent than BIA because it doesn't depend on hydration. A difference of 2–5% between methods is completely normal.

What is lean body mass and why does it matter? ▾

Lean body mass (LBM) is everything in your body that isn't fat — muscle, bone, water, organs, and connective tissue. It's also called fat-free mass. LBM matters because muscle tissue is metabolically active (it burns calories at rest), it determines your strength and athletic performance, and it predicts long-term health outcomes more strongly than weight alone. When you diet without exercising, you lose both fat and muscle. Tracking LBM alongside body fat % helps you ensure you're losing fat, not muscle.

How often should I measure my body fat? ▾

Once a week is ideal for tracking progress, always at the same time (morning, before eating) under the same conditions. Body fat doesn't change daily — meaningful changes take 4–8 weeks of consistent diet and exercise. Measuring too frequently leads to discouragement from normal fluctuations. Many fitness coaches recommend monthly measurements for people just starting out, and weekly for those actively cutting or bulking. What matters is the trend over 4–12 weeks, not any single reading.

How to Calculate Your Body Fat Percentage

Estimate body fat percentage using the Navy method — no calipers or scales required.

Take your measurements

You'll need waist, neck, and hip (women only) circumference. Use a flexible tape measure first thing in the morning before eating. Measure at the same spots each time.

Measure waist at the narrowest point

For most people this is about an inch above the belly button. Don't suck in — measure relaxed.

Enter your height and measurements

Select metric or imperial, enter all values, and your body fat percentage calculates instantly.

Interpret your result

The calculator shows your category (essential fat, athlete, fitness, acceptable, obese) and your estimated lean mass vs fat mass in kg/lbs.

Track changes over time

Body fat changes slowly — retest every 4–6 weeks. A 1–2% change over a month represents significant progress.

💡

💡 The Navy method is less accurate than DEXA scans but far more practical. It's most useful for tracking trends over time rather than as an absolute number.

Body FatCalculator

Why body fat % is more useful than BMI

How the US Navy Method works

What is a healthy body fat percentage?

Body fat vs BMI: when each is better

Body Fat
Calculator