health calculator

Body Fat Calculator

Estimate body fat percentage from common measurements.

Formula Verified by Dr. Sarah Jenkins, PhD

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Sex

Heightin

Neckin

Waistin

Hipin

Results

Estimated body fat

11.1%

MethodUS Navy estimate

Waist measurement34.0 in

Height used70.0 in

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Save this page to track changes in your body composition and verify whether weight changes reflect fat loss or muscle gains.

Formula

US Navy body fat method

Body fat % = 495 / density estimate - 450

The US Navy method estimates body fat from height, neck, waist, and hip measurements. It is useful for tracking trends, not medical diagnosis.

Step by step

How the calculation works

1Measure height, neck, waist, and hip consistently.
2Apply the sex-specific Navy circumference equation.
3Convert body density estimate into a body fat percentage.
4Use the result as a practical trend indicator.

Example

Example body fat estimate

A 70-inch male with a 34-inch waist and 15-inch neck is estimated near 18% body fat using the Navy method.

Related guides

Learn more about this calculation

Guide

Body Fat Percentage: How to Measure and What the Numbers Mean

Understand body fat percentage, how the US Navy method works, where smart scales and DEXA differ, and how to interpret results carefully.

Guide

BMI Calculation Guide: Formula, Ranges, and Limits

Calculate adult BMI by hand, understand the standard ranges, and learn why BMI is a screening measure rather than a diagnosis.

Metabolism Guide

Understanding BMR & Daily Calorie Burning

Learn the mathematical difference between BMR and TDEE, and how height, weight, and muscle mass affect metabolism.

How to understand and use this calculator

Understanding Body Fat Percentage

Body fat percentage is the total mass of fat divided by total body mass, expressed as a percentage. Unlike weight or BMI, body fat percentage directly details body composition, separating fat-free mass (muscle, bone, organs, water) from adipose tissue.

Adipose tissue is split into two categories: Essential Fat (necessary for hormone production, insulation, and organ protection, averaging 3% in men and 12% in women) and Storage Fat (excess energy reserves stored under the skin and around organs). Tracking body composition is critical because high levels of visceral storage fat are directly linked to metabolic issues.

The US Navy Circumference Method Formulas

While hydrostatic weighing and DEXA scans are the gold standards for body composition testing, the US Navy Circumference Method is a widely validated, cost-free alternative that uses body circumferences to estimate fat levels.

The mathematical equations are divided by biological sex to account for differences in fat distribution patterns (men typically accumulate fat around the waist, while women store fat around the hips and waist):

Metric Formulas (dimensions in cm, height in cm):

$$\text{Men: Body Fat (\%)} = 86.010 \times \log_{10}(\text{abdomen} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76$$

$$\text{Women: Body Fat (\%)} = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387$$

Imperial Formulas (dimensions in inches):

$$\text{Men: Body Fat (\%)} = 86.010 \times \log_{10}(\text{abdomen} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76$$ (using converted log scales)

$$\text{Women: Body Fat (\%)} = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387$$ (using log conversions)

Proper Measurement Technique for Accuracy

Circumference-based calculations rely heavily on precise measurements. To ensure accuracy:

* Neck: Measure immediately below the larynx, pulling the tape flat without compressing the neck.

* Abdomen/Waist (Men): Measure horizontally at the level of the navel.

* Waist (Women): Measure horizontally at the narrowest point of the torso (above the navel).

* Hips (Women): Measure horizontally at the widest point of the gluteal muscles.

Use a flexible, non-elastic tape measure pulled flat against the skin.

Body Fat Health Categories and Risks

The American Council on Exercise (ACE) classifies body fat percentages into standard categories:

* Essential Fat: 2-5% (Men), 10-13% (Women). Below this leads to organ failure and hormonal collapse.

* Athletes: 6-13% (Men), 14-20% (Women). Typical for highly trained competitive individuals.

* Fitness: 14-17% (Men), 21-24% (Women). A healthy, athletic composition.

* Average / Acceptable: 18-24% (Men), 25-31% (Women). Standard health ranges.

* Obese: 25%+ (Men), 32%+ (Women). Associated with high risks of cardiovascular issues.

Related concepts

Lean Mass

Total body weight minus fat mass, representing muscle, organs, bones, and water.

FMI

Fat Mass Index: fat mass divided by height squared, a scale-independent measure of fatness.

Android Fat Distribution

Fat accumulation primarily around the abdomen, typical for men and carrying higher health risks.

Frequently Asked Questions

What is the US Navy Circumference Method?+

It is a mathematical formula developed by the US Navy that uses height and neck, waist, and hip circumferences to estimate body fat percentage.

How accurate is the US Navy method?+

When measured correctly, the Navy method is accurate to within 3% to 4% of hydrostatic weighing, making it an excellent free alternative.

Why does the formula require hip measurements for women but not men?+

Biologically, women store more subcutaneous fat around the hips and thighs (gynoid distribution), while men store fat primarily around the midsection (android distribution).

What is essential fat?+

Essential fat is the minimum fat required for basic physiological functions, hormone regulation, and insulation (approx. 3% for men and 12% for women).

What is visceral fat?+

Visceral fat is fat stored deep inside the abdominal cavity around major organs, which is highly linked to metabolic issues and heart disease.

How often should I measure my body fat?+

Measure once every 2 to 4 weeks. Body fat changes slowly, and weekly measurements can be distorted by water retention.

Does this calculator tell me my lean mass?+

Yes. The calculator calculates your Fat Mass and Lean Mass weights based on your total body weight and body fat percentage.

How do I lower my body fat percentage?+

Maintain a moderate caloric deficit, consume adequate protein to preserve muscle, and engage in resistance training to burn fat while retaining lean mass.

Can I have too low a body fat percentage?+

Yes. Dropping below essential fat levels can cause hormonal collapse, heart arrhythmias, bone loss, and reproductive issues (amenorrhea) in women.

What is the best way to measure body composition?+

A DEXA (Dual-Energy X-ray Absorptiometry) scan is the clinical gold standard, tracking fat, bone density, and muscle mass by body segment.

How to understand and use this calculator

Understanding Body Fat Percentage

The US Navy Circumference Method Formulas

Metric Formulas (dimensions in cm, height in cm):

$$\text{Men: Body Fat (\%)} = 86.010 \times \log_{10}(\text{abdomen} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76$$

$$\text{Women: Body Fat (\%)} = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387$$

Imperial Formulas (dimensions in inches):

$$\text{Men: Body Fat (\%)} = 86.010 \times \log_{10}(\text{abdomen} - \text{neck}) - 70.041 \times \log_{10}(\text{height}) + 36.76$$ (using converted log scales)

$$\text{Women: Body Fat (\%)} = 163.205 \times \log_{10}(\text{waist} + \text{hip} - \text{neck}) - 97.684 \times \log_{10}(\text{height}) - 78.387$$ (using log conversions)

Proper Measurement Technique for Accuracy

Circumference-based calculations rely heavily on precise measurements. To ensure accuracy:

* Neck: Measure immediately below the larynx, pulling the tape flat without compressing the neck.

* Abdomen/Waist (Men): Measure horizontally at the level of the navel.

* Waist (Women): Measure horizontally at the narrowest point of the torso (above the navel).

* Hips (Women): Measure horizontally at the widest point of the gluteal muscles.

Use a flexible, non-elastic tape measure pulled flat against the skin.

Body Fat Health Categories and Risks

The American Council on Exercise (ACE) classifies body fat percentages into standard categories:

* Essential Fat: 2-5% (Men), 10-13% (Women). Below this leads to organ failure and hormonal collapse.

* Athletes: 6-13% (Men), 14-20% (Women). Typical for highly trained competitive individuals.

* Fitness: 14-17% (Men), 21-24% (Women). A healthy, athletic composition.

* Average / Acceptable: 18-24% (Men), 25-31% (Women). Standard health ranges.

* Obese: 25%+ (Men), 32%+ (Women). Associated with high risks of cardiovascular issues.

Related concepts

Lean Mass

Total body weight minus fat mass, representing muscle, organs, bones, and water.

FMI

Fat Mass Index: fat mass divided by height squared, a scale-independent measure of fatness.

Android Fat Distribution

Fat accumulation primarily around the abdomen, typical for men and carrying higher health risks.

Frequently Asked Questions

What is the US Navy Circumference Method?+

It is a mathematical formula developed by the US Navy that uses height and neck, waist, and hip circumferences to estimate body fat percentage.

How accurate is the US Navy method?+

When measured correctly, the Navy method is accurate to within 3% to 4% of hydrostatic weighing, making it an excellent free alternative.

Why does the formula require hip measurements for women but not men?+

Biologically, women store more subcutaneous fat around the hips and thighs (gynoid distribution), while men store fat primarily around the midsection (android distribution).

What is essential fat?+

Essential fat is the minimum fat required for basic physiological functions, hormone regulation, and insulation (approx. 3% for men and 12% for women).

What is visceral fat?+

Visceral fat is fat stored deep inside the abdominal cavity around major organs, which is highly linked to metabolic issues and heart disease.

How often should I measure my body fat?+

Measure once every 2 to 4 weeks. Body fat changes slowly, and weekly measurements can be distorted by water retention.

Does this calculator tell me my lean mass?+

Yes. The calculator calculates your Fat Mass and Lean Mass weights based on your total body weight and body fat percentage.

How do I lower my body fat percentage?+

Maintain a moderate caloric deficit, consume adequate protein to preserve muscle, and engage in resistance training to burn fat while retaining lean mass.

Can I have too low a body fat percentage?+

Yes. Dropping below essential fat levels can cause hormonal collapse, heart arrhythmias, bone loss, and reproductive issues (amenorrhea) in women.

What is the best way to measure body composition?+

A DEXA (Dual-Energy X-ray Absorptiometry) scan is the clinical gold standard, tracking fat, bone density, and muscle mass by body segment.

Body Fat Calculator

Inputs

Results

Bookmark this Body Fat Calculator

US Navy body fat method

How the calculation works

Example body fat estimate

Learn more about this calculation

Body Fat Percentage: How to Measure and What the Numbers Mean

BMI Calculation Guide: Formula, Ranges, and Limits

Understanding BMR & Daily Calorie Burning

Body Fat Calculator

Inputs

Results

Bookmark this Body Fat Calculator

Key output metrics

Body composition split

Fitness category thresholds

How to understand and use this calculator

Understanding Body Fat Percentage

The US Navy Circumference Method Formulas

Proper Measurement Technique for Accuracy

Body Fat Health Categories and Risks

Related concepts

Frequently Asked Questions

US Navy body fat method

How the calculation works

Example body fat estimate

Learn more about this calculation

Body Fat Percentage: How to Measure and What the Numbers Mean

BMI Calculation Guide: Formula, Ranges, and Limits

Understanding BMR & Daily Calorie Burning

Key output metrics

Body composition split

Fitness category thresholds

How to understand and use this calculator

Understanding Body Fat Percentage

The US Navy Circumference Method Formulas

Proper Measurement Technique for Accuracy

Body Fat Health Categories and Risks

Related concepts

Frequently Asked Questions