Estimate body fat percentage using the US Navy method
Essential Fat
Athlete
Fitness
Average
Obese
US Navy Method
The US Navy body fat formula uses circumference measurements to estimate body fat percentage. It is widely used by military organizations for fitness assessments.
What is a Body Fat Calculator?
A body fat calculator estimates your body-fat percentage from tape measurements - neck, waist, and (for women) hips - plus your height, using the US Navy method. Unlike weight alone, it reveals the balance of fat and muscle: two people at the same weight can look very different and carry very different health risks depending on their body fat. Body-fat percentage reflects body composition more directly than BMI, which is why it is valued in fitness and health settings. The big advantage of this method is that it needs only a household tape measure, so you can track your approximate level and changes without a body-composition scale or a precise DEXA scan. It helps you check whether weight loss is coming from fat while you preserve muscle.
How to Use
1. Select your sex.
2. Enter your height (cm), neck circumference (cm), and waist circumference (cm). Women also enter hip circumference (cm).
3. Calculate to see your estimated body-fat percentage.
Measuring tips: take the neck just below the larynx, the waist at navel height (women at the narrowest point), and the hips at their widest. Keep the tape level and snug without compressing, and measure at the same time and conditions to track changes.
Formula & Definition
The tool uses the US Navy method (centimeters, base-10 logarithms):
Men: body fat % = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
Women: body fat % = 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.221 x log10(height)) - 450
It estimates body density from the circumference differences and then converts that to a fat percentage. There are also simpler estimates from BMI (such as the Deurenberg equation), but the circumference-based Navy method tends to reflect body shape more closely.
Interpreting Results
As a general guide, a healthy range is roughly 10-20% for men and 18-28% for women; women are naturally higher because of reproductive function. Athletes run lower, but dropping below essential fat (about 3% for men, 12% for women) harms health, while very high body fat raises the risk of chronic disease. The Navy method is only an estimate from tape measurements and can differ by a few percentage points from precise methods like DEXA or hydrostatic weighing. Posture and how tightly you pull the tape also change the reading, so focus on the trend rather than the absolute value. If your weight drops during a diet but your body-fat percentage does not, you may be losing muscle.
Frequently Asked Questions
How accurate is the US Navy method? ▾
It is a convenient estimate from circumferences and can differ by a few percentage points from precise methods like DEXA. Keeping conditions consistent makes it reliable for tracking trends.
What is a healthy body-fat percentage? ▾
Roughly 10-20% for men and 18-28% for women. Women are naturally higher for reproductive function, and dropping below essential fat is dangerous.
Any tips for measuring accurately? ▾
Measure the neck below the larynx, the waist at navel height, and the hips at their widest, keeping the tape level. Avoid pulling too tight or loose, and use the same time and conditions for comparisons.
Should I look at BMI or body fat? ▾
BMI is a quick measure from height and weight; body-fat percentage directly shows the proportion of fat. Body fat is more useful for understanding body composition since it is less affected by muscle mass.
The body-fat percentage shown is an estimate and does not replace measurement by medical equipment or a diagnosis. Consult a doctor or qualified professional to assess your health or plan weight loss.