Body Fat Calculator | OmniCalculator

  • Adam
  • November 1, 2025

Free body fat percentage calculator using US Navy circumference method and BMI formula. Calculate body fat mass and lean mass with health categories.

📏 💪 📏

Body Fat Calculator

Calculate your body fat percentage using the US Navy method and BMI method. Track your body composition and fitness progress.

📋 Quick Navigation

📏 Enter your measurements to calculate body fat! 💪
18 - 100 years
in cm
in kg
in cm (below larynx)
in cm (at navel/smallest)
18 - 100 years
in cm
in kg
Body Fat Percentage
0%
Calculating...
Essential Athletes Fitness Average Obese

Body Fat %

0%
percentage

Body Fat Mass

0
kg

Lean Body Mass

0
kg

Category

—
fitness level

📊 Calculation Results

Measurement Method Result
Body Fat % US Navy 0%
Body Fat Mass Calculated 0 kg
Lean Body Mass Calculated 0 kg
Health Category Male Fitness

🧮 Body Fat Calculation Formulas

US Navy Method (Most Accurate)

Developed by the Naval Health Research Center, this circumference-based method is highly accurate (~3.5% error) and widely used.

For Men (metric):
BF% = 495 / (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450

For Women (metric):
BF% = 495 / (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450

All measurements in centimeters

Body Fat Mass Calculation

Once you have body fat percentage, calculate actual fat mass and lean mass.

Body Fat Mass = Weight × (Body Fat % / 100)
Lean Body Mass = Weight − Body Fat Mass

Example: 75 kg person with 20% body fat
Body Fat Mass = 75 × 0.20 = 15 kg
Lean Body Mass = 75 − 15 = 60 kg

BMI-Based Method (Simpler)

Uses height, weight, and age. Less accurate but simpler than Navy method.

For Men:
BF% = (1.20 × BMI) + (0.23 × Age) − 16.2

For Women:
BF% = (1.20 × BMI) + (0.23 × Age) − 5.4

BMI = Weight (kg) / Height (m)²

📋 Body Fat Standards & Categories

American Council on Exercise (ACE) Standards

Category Men Women
Essential Fat 2-5% 10-13%
Athletes 6-13% 14-20%
Fitness 14-17% 21-24%
Average 18-24% 25-31%
Obesity 25%+ 32%+

Age-Based Ideal Body Fat (Jackson & Pollock)

Age Men Women
20 8.5% 17.7%
25 10.5% 18.4%
30 12.7% 19.3%
35 13.7% 21.5%
40 15.3% 22.2%
45 16.4% 22.9%
💡 Important: Essential fat is necessary for organ protection and hormone production. Men need 2-5%, women need 10-13% minimum for health.

📏 How to Take Accurate Measurements

General Guidelines

  • Measure on bare skin (not over clothing)
  • Use a flexible, non-stretchable measuring tape
  • Keep tape parallel to ground
  • Tape should be snug but not compressing skin
  • Measure to nearest 0.5 cm for accuracy
  • Take measurements before exercise
  • Take measurements at same time each day

Neck Measurement

Position: Below the larynx (Adam's apple). Technique: Measure horizontally around the neck, keeping tape perpendicular. Common Mistake: Don't include the jaw or flare your neck outward.

Waist Measurement

For Men: At the level of the belly button (navel). For Women: At the smallest horizontal width of your waist. Important: Don't pull your stomach inward - relax and breathe naturally!

Hip Measurement (Women Only)

Position: At the widest point of the hip/buttocks. Technique: Stand facing forward with feet together. Measure horizontally around the fullest part.

Height Measurement

Position: Stand barefoot, heels against wall, eyes forward. Technique: Measure from floor to top of head with tape vertical. Consistency: Height can vary slightly throughout the day (up to 1-2 cm taller in morning).

📌 Accuracy Tip: Have someone else take your measurements if possible, as self-measurement can introduce errors. Take 2-3 measurements and average them for best results.

❓ Frequently Asked Questions

Which method is more accurate: Navy or BMI? +
The US Navy method is more accurate (~3.5% error) because it uses circumference measurements that better account for body composition. BMI method (~5-10% error) is simpler but less precise. Navy method is recommended for fitness tracking.
Why is body fat percentage important? +
Body fat percentage is a better health indicator than weight or BMI alone because it distinguishes between muscle and fat. Two people of same weight can have very different body composition and health. Tracking body fat shows real fitness progress!
What's the difference between circumference-based and DEXA? +
DEXA (X-ray based) is more accurate (~±2%) but expensive ($100-300). Circumference methods (Navy) are accurate within ±3.5%, free, and convenient. For most fitness tracking, Navy method is sufficient. DEXA is better for medical purposes.
Can body fat decrease without weight loss? +
Yes! Through strength training + adequate nutrition, you can build muscle while losing fat. The scale stays similar but your body composition improves. This is why body fat % is more meaningful than weight alone for fitness goals.
How often should I measure my body fat? +
Measure monthly for best tracking. Weekly measurements show fluctuations from hydration and digestion. Significant changes take 4-6 weeks to measure. Consistency in time of day and technique is important for accurate trend tracking.
Is some body fat necessary? +
Yes! Essential fat (2-5% men, 10-13% women) is necessary for brain, heart, hormone production, and organ protection. Going below essential fat is unhealthy and dangerous. Never aim for 0% body fat!
Why do women have higher essential fat than men? +
Women have ~6% more essential body fat due to biological differences related to reproduction, lactation, and hormone production. This is completely normal and healthy - not a disadvantage. Both genders need their respective essential fat minimums.
How does age affect body fat? +
Body fat naturally increases 0.5-1% per decade after age 30 due to metabolic slowdown and muscle loss. However, this is largely preventable through resistance training, adequate protein, and consistent exercise. Older adults can maintain low body fat with effort!

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