Body Fat Calculator

The U.S. Navy method estimates body fat from circumference measurements. For men it uses height, neck, and waist; for women it adds hip. The formulas apply logarithms to those measurements and are accurate to about plus or minus 3-4% compared to clinical methods.

The Navy method is one of the most convenient field methods and is typically within 3-4% of DEXA or hydrostatic weighing. For best accuracy, measure first thing in the morning, use a soft tape, and take each measurement two to three times and average the results.

For men, 10-20% is generally healthy (below 6% is essential fat only); for women, 18-28% is healthy (below 14% is essential fat only). This calculator places you in a category from Essential Fat through Athlete, Fitness, Average, or Obese.

It is one of the better tape-based methods, typically within 3-4% of DEXA. It tends to overestimate lean, muscular builds and underestimate very high body fat, and it cannot distinguish subcutaneous from visceral fat. Accuracy depends heavily on consistent measuring technique, so measure at the same landmarks each time, ideally in the morning before eating.

Body fat percentage is the more meaningful number because BMI only compares weight to height and cannot tell muscle from fat. A muscular athlete can register "overweight" on BMI while having low body fat, and someone with a normal BMI can still carry too much visceral fat ("normal weight obesity"). Use BMI as a quick screen and body fat percentage when you want a truer picture of composition.

Measure the neck just below the larynx (Adam's apple) keeping the tape horizontal and relaxed, and the waist at the navel for men or the narrowest point for women, exhaling normally without pulling the tape tight. For the hip, measure the widest point around the buttocks. Stand relaxed, use a soft non-stretch tape, and average two or three readings to reduce error.

Essential fat is the minimum needed for normal hormone, reproductive, and cellular function - about 2-5% for men and 10-13% for women. Dropping below it risks hormone disruption, low energy, and nutrient deficiencies, so it is not a healthy target outside of brief, supervised contest prep. Most active adults feel and perform best well above the essential floor.

Every 2-4 weeks is plenty - body fat changes slowly, and day-to-day water shifts add noise. Keep the measuring conditions consistent (same time of day, same tape, same landmarks) and watch the trend rather than any single reading. Combine it with photos and how your clothes fit for the clearest picture.

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