Body Fat Calculator

Estimate your body fat percentage using the U.S. Navy method or the BMI-based Deurenberg formula. Understand your body composition to optimise your fasting strategy.

Sex

Age

Method

Height

Waist circumference (at navel)

Neck circumference

Weight (optional — for fat/lean mass)

Body fat percentage is a far more meaningful measure of health and fitness than weight alone. Two people at the same weight can look completely different and face very different health risks depending on their body composition.

For those practising intermittent fasting, tracking body fat gives you a clearer picture of whether your fasting protocol is working. Scale weight can fluctuate with water retention, but body fat percentage reveals the true changes happening beneath the surface.

Frequently Asked Questions

How accurate is the US Navy body fat method?

The US Navy method is accurate to within about 3-4% of DEXA scan results for most people. It uses circumference measurements of the neck, waist, and hips to estimate body fat. While not as precise as clinical methods, it is reliable for tracking changes over time.

What is a healthy body fat percentage?

For men, 10-20% is generally considered healthy, with 14-17% being the fitness range. For women, 18-28% is healthy, with 21-24% as the fitness range. Essential fat minimums are about 2-5% for men and 10-13% for women.

Does intermittent fasting reduce body fat specifically?

Research suggests that intermittent fasting can be particularly effective at reducing visceral fat (the dangerous fat around organs) compared to standard calorie restriction alone. IF may also help preserve lean muscle mass during weight loss, improving your overall body composition.

What is the difference between body fat percentage and BMI?

BMI is a simple ratio of weight to height and does not distinguish between muscle and fat. Body fat percentage measures the actual proportion of fat in your body. A muscular person could have a high BMI but a low body fat percentage, making body fat the more useful metric.