Body Fat Calculator

How to Use This Body Fat Calculator

Select units and sex, then enter your tape measurements. The US Navy method uses waist, neck, and height for men, and adds hip circumference for women. Results are best treated as estimates—use consistent measurement technique if you’re tracking change over time.

• Measure consistently (same landmarks, same tape tension, similar time of day).
• Repeat and average 2–3 readings per site if you want a steadier estimate.
• Use trends instead of reacting to single measurements.

What Body Fat Percentage Represents

Body fat percentage estimates how much of your total body weight is fat tissue versus lean tissue (muscle, bone, organs, and body water). Compared to BMI, it’s closer to “body composition,” but it’s still an approximation—especially when based on tape measurements.

How the US Navy Method Works

The US Navy circumference method uses logarithmic equations that combine height with circumference measurements. The idea is that fat distribution (especially around the waist) is often correlated with total body fat, but individual variation can be large.

• Men: waist, neck, and height
• Women: waist, neck, hip, and height

Typical Category Ranges

Category ranges vary by source and population. These are broad, commonly referenced adult ranges used for general context—not a diagnosis and not a performance verdict.

• Men (broad reference): Athletes often lower, general population commonly higher depending on age and activity.
• Women (broad reference): Typically higher than men due to physiological differences, with wide normal variation.

Why Estimates Can Vary

Tape placement differences, posture, hydration, food volume, and normal day-to-day fluctuation can change measurements. Two people can share the same estimated percentage and still look or perform very differently depending on muscle mass, fat distribution, and training history.

Interpreting Results in Context

A practical approach is to treat body fat percentage as one reference point alongside consistent indicators such as waist trends, performance, how clothing fits, and longer-term weight trends. If you want related estimates, you can compare this tool with the BMI Calculator, explore energy needs via the TDEE Calculator, and translate calorie targets into ranges using the Macro Calculator and Protein Calculator.

Common Misinterpretations (And What This Estimate Can’t Tell You)

Body fat percentage is a useful concept, but tape-based estimates are often misunderstood. The US Navy method is best treated as a trend-friendly approximation, not a precise lab measurement.

• “This is my exact body fat %.” Tape methods can be off for individuals. The most reliable use is comparing results using the same technique over time.
• “A small change means I gained/lost fat.” Measurement error, posture, hydration, and normal day-to-day fluctuation can move circumferences without real tissue change.
• “Category labels are universal and objective.” Category ranges vary by source and population. Treat labels as broad context—not a diagnosis or a performance verdict.
• “Two people with the same % will look the same.” Muscle mass, fat distribution, bone structure, and height can change appearance dramatically at the same estimated percentage.
• “If the number is higher, I’m automatically unhealthy.” Health and performance depend on many factors. Body fat % is one indicator, not the full picture.
• “This method works equally well for everyone.” People with atypical fat distribution, very high muscularity, or measurement difficulties may see larger error.
• “My waist measurement equals belly fat.” Waist circumference can reflect fat, but also digestion, water retention, and how tightly/where the tape is placed.

When Another Method Is More Useful

If you want the most precision, lab-style methods (for example, DEXA or hydrostatic weighing) are typically used in clinical or research contexts, but they’re not always necessary for day-to-day tracking. For most people, the most practical approach is combining consistent tape technique with repeatable trend signals (such as waist trends, performance, and longer-term weight patterns). If you want a separate reference point, compare your result with the BMI Calculator and explore energy needs with the TDEE Calculator.

Body Fat Calculator FAQ

How accurate is this body fat calculator?

The US Navy method can be a practical estimate for many adults when measurements are taken carefully and consistently. It is still an estimate and can be off for individuals with atypical fat distribution or measurement inconsistency.

Why does my result change if I re-measure?

Small differences in tape placement and tension can change circumference values. Hydration, posture, and normal daily fluctuation can also shift measurements. If you’re tracking, use consistent technique and focus on trends.

Do you store my data?

No. This calculator runs locally in your browser. No account is required and no personal data is collected.

Reviewed & Updated

Calculator logic and on-page content reviewed for clarity and educational accuracy. Last review: December 2025.