How to use
- Tap Male or Female.
- Enter height and circumferences in centimeters—women also enter hip.
- Follow the short hints under neck/waist/hip fields so each measurement uses the same technique every time.
- Read estimated body fat % and the screening band on the right; compare trends over weeks, not one reading.
Method
U.S. Navy circumference equations (log of waist−neck or waist+hip−neck with height). Not DEXA or hydrostatic testing. For height/weight-only screening, see BMI; for daily calories after composition goals, see calorie calculator.
Example inputs (male)
175 cm height, neck 38 cm, waist 85 cm → Navy estimate often near high-teens to low-20s % body fat depending on exact tape reading. Switch to Female and add hip (e.g. 95 cm) to use the women’s equation.
When results look “wrong”
Muscular lifters may read higher than DEXA because thick neck/waist still carry little fat. Very high outputs often trace to waist measured at the wrong level or hip omitted for women.
Tracking progress
Measure same time of day, same hydration, same tape path. A 1–2 percentage-point drift over a month matters more than chasing daily changes.
How do I calculate body fat with the Navy method?
Enter sex, height (cm), neck (cm), and waist (cm). Women also enter hip (cm). The page converts to inches internally and applies the published Navy log formulas. Example male 175 cm tall, neck 38 cm, waist 85 cm often lands in mid-teens to low-20s %—your row updates live.
How should I measure neck, waist, and hip?
Neck: narrowest below the larynx, tape level. Waist: navel level, relaxed abdomen, tape parallel to the floor. Hip (women): widest glutes/hips. Measure twice and average if you are unsure; bloating and hydration can shift waist by a centimeter or two.
Why does the calculator say waist must be larger than neck?
The men’s Navy equation uses log10(waist − neck). If waist is not greater than neck, the math is invalid—usually a tape placement error or transposed numbers.
Why is hip required for women but not men?
The sex-specific Navy formulas differ. Women’s equation includes waist + hip − neck; men’s uses waist − neck with height only.
Body fat calculator vs BMI—which should I use?
BMI uses height and weight only. This page adds shape via circumferences—two people with the same BMI can differ in fat if muscle mass differs. Neither replaces clinical body-composition testing.
Are the category labels (athlete, fitness, average) accurate for me?
They are ACE-style screening bands applied to the Navy % estimate. Lifters, ethnicity, age, and measurement error can misclassify individuals—use trends and professional methods if decisions matter medically.
Can I use this for medical diagnosis?
No. DEXA, hydrostatic weighing, or clinical BIA are appropriate when precision matters. This page is a free planning/screening estimate.
Inches instead of centimeters?
This form expects cm. Divide inches by 2.54 or use the length converter, then paste centimeters here.
What do the screening bands mean?
Essential / athlete / fitness / average / obese labels map the Navy % to common ACE-style charts separately for men and women—they describe the estimate, not your health outcome.
Male 180 cm, neck 40, waist 90—roughly what %?
Often low-to-mid 20s % with the Navy method—enter exact numbers on the form. Waist must exceed neck or the tool will ask you to remeasure.
Switch sex after entering numbers?
Female mode requires hip; male mode ignores hip. Toggle sex and fill the fields that appear—results update immediately.