Body Fat Calculator
Calculate Your Body Fat Percentage
Body composition
What Is Body Fat Percentage?
Body fat percentage tells you what portion of your total body weight is fat. Unlike BMI, it looks directly at body composition by separating fat mass from lean body mass.
Getting started
How to Use This Body Fat Calculator
Use accurate circumference measurements and read the result as an estimate, not a laboratory measurement.
- 1
Select gender
The Navy formulas use different circumference inputs for men and women.
- 2
Enter age and units
Choose metric or US standard units before entering measurements.
- 3
Input height and weight
Use current values for the most useful fat mass and lean mass estimate.
- 4
Measure neck and waist
Use a flexible tape and keep it level against the skin.
- 5
Add hip measurement if female
Hip circumference is required for the female Navy formula.
- 6
Review results
Read body fat percentage, fat mass, lean mass, and category together.
The math
Fat Mass and Lean Body Mass
Once body fat percentage is estimated, the calculator can estimate fat mass and lean body mass from total body weight.
Fat mass formula
Calculates the total estimated weight of fatty tissue.
Lean body mass formula
Includes muscles, bones, organs, and water.
Methodology
U.S. Navy Circumference Formulas
This calculator estimates body fat percentage using the U.S. Navy Circumference method. The formulas are calculated in inches, with centimeters converted before the math runs.
| Formula | Equation |
|---|---|
| Men | 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76 |
| Women | 163.205 × log10(waist + hip - neck) - 97.684 × log10(height) - 78.387 |
Example
Body Fat Calculation Example
This example shows how body fat percentage becomes fat mass and lean mass.
| Metric | Value |
|---|---|
| Example person | 80 kg with 20% body fat |
| Fat mass | 80 × 20 / 100 = 16 kg |
| Lean body mass | 80 - 16 = 64 kg |
| Meaning | Fat mass is stored fat; lean mass includes muscle, bone, organs, and water. |
Classifications
ACE Body Fat Categories
A commonly used body composition standard is the American Council on Exercise categorization. Women naturally require more essential fat for hormonal and physiological functions.
| Category | Women | Men |
|---|---|---|
| Essential fat | 10-13% | 2-5% |
| Athletes | 14-20% | 6-13% |
| Fitness | 21-24% | 14-17% |
| Average | 25-31% | 18-24% |
| Obese | 32%+ | 25%+ |
Measurement guide
How to Measure Correctly
Small deviations in waist, neck, or hip alignment can skew the final Navy equation result.
- Neck circumference
- Wrap the tape horizontally around the neck, just below the larynx. Keep your neck relaxed and look forward.
- Waist circumference
- For men, measure around the waist at navel level. For women, measure at the narrowest natural waistline.
- Hip circumference
- For women, wrap the tape around the widest part of the hips and gluteal muscles.
- Measurement quality
- Stand relaxed, keep the tape flat, do not compress the skin, take 2-3 measurements, and use the average.
Metric comparison
Body Fat Percentage vs BMI
BMI is a fast height-to-weight screening tool. Body fat percentage is more specific because it estimates adipose tissue instead of total mass.
- Body Fat Percentage
- Body fat percentage estimates how much of your weight is fat tissue. It separates fat mass from lean body mass.
- BMI
- BMI uses only height and weight. It is fast, but it cannot distinguish high muscle density from high body fat.
Clinical limits
Accuracy and Other Assessment Methods
The Navy circumference method is a practical estimate, not a direct laboratory measurement. Hydration, bloating, fat distribution, and measurement placement can affect results.
- DEXA scan
- Clinical imaging that maps bone, fat, and lean mass with high accuracy.
- Bioelectrical impedance
- Common in smart scales but highly influenced by hydration.
- Skinfold calipers
- Can be accurate when performed by an experienced practitioner.
- Hydrostatic weighing
- Underwater weighing that estimates body density in a lab setting.
- Bod Pod
- Uses air displacement to estimate volume and density.
- Waist-to-height ratio
- Simple screening metric for abdominal and metabolic risk context.
Next checks
Use Body Fat with Other Calculators
Body fat estimates are stronger when paired with BMI, ideal weight, calories, macros, BMR, and TDEE.
Frequently Asked Questions
The American Council on Exercise considers 21–32 percent body fat healthy for adult women and 14–24 percent healthy for adult men. Athletes can be lower (14–20 percent for women, 6–13 percent for men), and essential fat is roughly 10–13 percent for women and 2–5 percent for men.
We use the US Navy method (Hodgdon-Beckett formula), which estimates body fat from height and circumference measurements (neck, waist, and — for women — hips). It is one of the most accessible methods and typically falls within 3–4 percentage points of more advanced techniques like DEXA.
It is reasonably accurate for most adults (mean error around 3–4 percentage points compared to DEXA) and far cheaper. For higher precision, consider DEXA scans, hydrostatic weighing, or air displacement plethysmography (Bod Pod).
BMI is a ratio of weight to height and does not separate muscle from fat. Body fat percentage directly measures the proportion of fat in your body, which is a much better indicator of metabolic health. Two people with identical BMI can have very different body fat percentages.
Combine a moderate calorie deficit (10–20 percent below maintenance) with adequate protein (1.6–2.2 g/kg of body weight), resistance training, and consistent sleep. Aim to lose no more than 0.5–1 percent of body weight per week to preserve lean mass.
Essential fat is the minimum your body needs for normal function (around 10–13 percent for women and 2–5 percent for men). Storage fat is the additional fat that accumulates in adipose tissue. Going below essential fat levels is unhealthy and can disrupt hormones and immune function.
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