How to use this calculator
Select your gender and preferred unit system, then enter your height, weight, and circumference measurements. The calculator uses the US Navy method to estimate your body fat percentage in real time.
For the most accurate results, use a flexible tape measure. Measure your waist at navel level, your neck just below the larynx (Adam's apple), and, for women, your hips at the widest point. Keep the tape level and snug without compressing the skin.
Body fat percentage vs. BMI
BMI (Body Mass Index) is calculated from height and weight alone. It cannot distinguish between muscle and fat, which means a muscular person and an overfat person of the same height and weight get the same BMI score. Body fat percentage addresses this limitation by estimating how much of your total weight is fat tissue versus lean mass.
That said, no single metric tells the whole story. The US Navy method is a convenient estimate, but it's still an approximation based on circumference measurements. DEXA scans, hydrostatic weighing, and air displacement plethysmography (Bod Pod) provide more precise body composition data. Use this calculator as a tracking tool and directional guide, not a clinical diagnosis.
Measurement technique matters
The accuracy of this method depends almost entirely on how consistently you take your measurements. Even a half-inch difference in tape placement can shift results by 1-2 percentage points.
Stand upright and relaxed. Don't suck in your stomach or flex your neck muscles. Measure at the same time of day each time you check, ideally in the morning before eating. If possible, have someone else take the measurements to reduce parallax error from reading the tape at an angle.
Understanding body fat categories
| Category | Men | Women | What it means |
|---|---|---|---|
| Essential Fat | 2-5% | 10-13% | Minimum fat needed for basic physiological function. Not sustainable long-term. |
| Athletic | 6-13% | 14-20% | Typical of competitive athletes. Visible muscle definition. |
| Fitness | 14-17% | 21-24% | Lean and healthy. Good muscle tone with some visible definition. |
| Average | 18-24% | 25-31% | Typical range for the general population. Adequate for health. |
| Obese | 25%+ | 32%+ | Elevated health risk. Associated with higher rates of chronic disease. |
Frequently asked questions
How does the US Navy body fat formula work?
The formula uses logarithmic relationships between circumference measurements (waist, neck, and hips for women) and height to estimate the proportion of body weight that is fat. It was developed by researchers Hodgdon and Beckett at the Naval Health Research Center.
How accurate is the Navy body fat method?
The Navy method is generally accurate within 3-4% compared to DEXA scans. Accuracy depends on consistent, correct tape placement. It works best for people with typical body proportions and may be less precise at the extremes of body composition.
What is a healthy body fat percentage?
For men, 14-17% is considered the fitness range, while 6-13% is athletic. For women, 21-24% is fitness and 14-20% is athletic. The "right" level depends on your goals, age, and overall health. Extremely low body fat can be just as harmful as extremely high body fat.
Is body fat percentage better than BMI?
Body fat percentage gives a more nuanced picture because it separates fat from lean mass. BMI can misclassify muscular people as overweight. However, both are screening tools, and neither replaces a comprehensive health assessment from a medical professional.