How the body Fat Calculator works
The Navy method estimates body fat from how circumference sites relate to height, using logarithmic formulas fitted against underwater weighing data. Men measure neck and waist; women add the hip. Done carefully, it tracks within a few points of lab methods.
Men: 86.010 log(waist − neck) − 70.041 log(height) + 36.76
Example: a man at 5 foot 10 with a 34 inch waist and 15 inch neck estimates near 17.5% body fat, which at 170 lb is about 30 lb of fat mass and 140 lb lean.
Frequently asked questions
How accurate is the tape method?
Within about 3 to 4 percentage points of lab measurement for most people when measurements are taken consistently. Its real strength is tracking change over time with the same technique.
How do I measure correctly?
Use a flexible tape, snug but not compressing skin, at the end of a normal exhale. Measure the same spots each time, ideally in the morning, and average two or three readings.
What are typical body fat ranges?
For men, fitness is commonly 14% to 17% and average 18% to 24%. For women, fitness 21% to 24% and average 25% to 31%. Essential fat sits near 3% for men and 12% for women.