Body Fat Percentage Calculator

What this body fat calculator does

It estimates your body fat percentage using the U.S. Navy circumference method — the same tape-measure formula the Naval Health Research Center validated and the military still uses for fitness assessments. Enter your height, neck, and waist (plus hip for women), and it returns your estimated body fat percentage, where that falls on the standard category scale, and your approximate fat mass and lean mass if you also enter your weight.

Who it's for

Anyone tracking body composition without access to a DEXA scan or calipers — gym-goers monitoring a cut or bulk, people starting a fitness program who want a baseline number, or anyone curious how their measurements stack up against standard fitness categories.

How to use it

• Select your gender — the formula (and the hip measurement it needs) differs between men and women.
• Choose US units (inches/lb) or metric (cm/kg).
• Measure your neck just below the larynx, your waist at the navel, and (for women) your hip at the widest point — keep the tape snug but not compressing the skin.
• Enter your height and those measurements; your body fat percentage and category update instantly.
• Add your weight too, and it'll break that percentage down into actual fat mass and lean body mass.

Real-world use cases

• Tracking progress during a cut or bulk: re-measure every few weeks and watch the percentage and lean mass trend, which tells you more than the scale alone.
• Getting a fitness baseline before starting a new training program, without needing gym equipment or a professional assessment.
• Checking military or athletic fitness standards that reference Navy-method body fat percentages directly.
• Comparing against BMI: body fat percentage tells a more complete story than BMI alone, especially for muscular or very lean people BMI tends to mislabel.

Frequently asked questions

How accurate is the Navy method?

Studies generally show it's accurate to within about 3–4% of body fat compared to more precise methods like DEXA scans, which makes it a solid free estimate — not a lab-grade measurement, but good enough to track trends over time.

Why does the formula need my neck measurement?

The Navy method uses the difference between waist and neck circumference (plus hip, for women) as a proxy for body fat, since that difference correlates strongly with fat distribution around the torso in validated studies.

What's a healthy body fat percentage?

For men, 14–17% is generally considered "fitness" level and 18–24% "average"; for women, the equivalent ranges are roughly 21–24% and 25–31%. Essential fat (the minimum needed for basic health) is about 2–5% for men and 10–13% for women.

Why do men and women use different formulas?

Body fat distribution differs by sex — women naturally carry more essential fat and store it differently around the hips, so the female formula includes a hip measurement the male formula doesn't need.

Is this the same as a BMI calculator?

No. BMI only uses height and weight and can't distinguish muscle from fat, which is why a muscular person can show as "overweight" on BMI alone. This calculator estimates actual body fat percentage from circumference measurements instead.