What is Body Fat Calculator?

The Body Fat Calculator estimates your body fat percentage using body measurements and standard formulas. This free tool helps you understand your body composition beyond just weight — all data stays private on your device.

The estimate uses the U.S. Navy circumference formula, which needs waist and neck measurements plus height (women also enter hip). Categories range from Essential Fat through Athletes, Fitness, Average, and Obese, with separate thresholds for men and women. A coloured bar shows where the number sits, so it is easier to spot whether a few weeks of training moved the needle.

How to use

1. Choose your gender and preferred measurement unit (inches or centimetres)
2. Provide waist, neck, and hip measurements as required
3. View your estimated body fat percentage and fitness category

When to use

• Tracking body composition during a cutting or bulking cycle when weight alone misleads you.
• Setting realistic gym goals before starting a new workout plan.
• Comparing a tape-and-mirror estimate against a future DEXA or InBody scan.

Result

A 30-year-old male with a 32-inch waist and 15-inch neck might have approximately 18% body fat.

FAQ

Which formula does the calculator use?

It uses the U.S. Navy circumference equation. For men it takes waist minus neck against height; for women it takes waist plus hip minus neck against height. Both forms then run through a logarithmic regression that the Navy validated against hydrostatic weighing. When you add weight, it also shows a BMI-based estimate (the Deurenberg formula) next to it so you can compare two independent methods.

How accurate is this method compared to a DEXA scan?

The Navy method is typically within 3 to 4 percentage points of DEXA for adults at average body fat. Accuracy slips at the extremes (very lean athletes or very obese ranges). DEXA, hydrostatic weighing, and the Bod Pod remain the clinical benchmarks.

Where exactly should I take the waist and neck measurements?

Waist for men: at the navel, relaxed (not sucked in). Waist for women: at the narrowest point above the navel. Neck: just below the larynx, sloping slightly downward toward the front. Use a flexible cloth tape held snug but not tight.

Why do men and women use different inputs?

Women carry more fat at the hips than men on average, so the female formula adds hip circumference to better fit the underlying body composition data. Men's equation only needs waist and neck because hip mass contributes less variance there.

Does my data leave the page?

No. Heights and measurements are processed on your device and never uploaded. Numbers vanish when you refresh or close the tab, so the calculator stays usable on a borrowed phone without leaving a trace.

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