Body Fat Calculator (U.S. Navy Method)
Enter your measurements below to estimate your body fat percentage. This is one of the most practical at-home methods and only requires a measuring tape.
Note: This tool provides an estimate. Hydration, tape placement, and posture can affect your result.
If you have ever asked, “How do I calculate body fat?” you are already asking a better question than simply “How much do I weigh?” Scale weight is useful, but body fat percentage gives you much more context about your health and progress.
Quick answer: the easiest way to calculate body fat at home
For most people, the best balance of simplicity and accuracy is the U.S. Navy method, which uses a tape measure and a formula. It is not perfect, but it is practical, repeatable, and far better than guessing by mirror alone.
- At home: U.S. Navy tape-measure method
- In clinics/gyms: DEXA scan, Bod Pod, hydrostatic weighing
- Portable option: Skinfold calipers (requires practice)
Method 1: U.S. Navy formula (what this calculator uses)
This approach estimates body fat from circumference measurements. It is one of the most common online methods because it only needs a soft tape measure.
Measurements you need
- Men: height, neck, waist
- Women: height, neck, waist, hips
Formulas
Men: Body Fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Women: Body Fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
Because these formulas were calibrated in inches, this page automatically converts centimeters to inches behind the scenes for better accuracy.
How to take body measurements correctly
Bad measurements lead to bad estimates. If you want useful results, consistency matters.
Best practices
- Measure at the same time of day (morning is best).
- Stand naturally, do not suck in your stomach.
- Keep the tape snug but not tight enough to compress skin.
- Take each measurement 2–3 times and average them.
- Track trends over weeks, not day-to-day changes.
What body fat percentage ranges mean
Body fat needs are different for men and women. Women naturally carry more essential fat for hormonal and reproductive health.
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese range | 25%+ | 32%+ |
Other ways to estimate body fat
1) DEXA scan
DEXA is often considered one of the most informative options because it can show regional fat distribution as well as bone density. It is more expensive and less available than tape methods.
2) Skinfold calipers
Calipers can be fairly accurate in trained hands, but technique errors are common when self-testing. If you use this method, have the same trained person perform each test.
3) Bioelectrical impedance scales
Smart scales are convenient, but hydration, food intake, and skin temperature can swing the number. Use them for trend tracking, not absolute precision.
Common mistakes when calculating body fat
- Comparing different methods as if they are identical (DEXA vs. tape vs. scale).
- Changing tape location each time.
- Measuring after workouts, large meals, or high-sodium days.
- Focusing on a single data point instead of a 6–12 week trend.
How often should you calculate body fat?
Every 2 to 4 weeks is enough for most people. Body composition changes slower than scale weight, especially if you are trying to build muscle while losing fat. Monthly measurements give a clearer signal and reduce frustration.
Bottom line
If your goal is to understand health and physique progress, learning how to calculate body fat is worth it. Use a repeatable method, measure consistently, and track trends over time. The number does not need to be perfect to be useful—what matters is whether your direction matches your goals.