How to Use the Body Fat Calculator
Body fat percentage is a better indicator of health and fitness than weight alone. This calculator gives a reasonable estimate without expensive equipment.
Step-by-Step Instructions
- 1 Select your gender.
- 2 Enter your height, neck circumference, and waist circumference.
- 3 For women, also enter hip circumference.
- 4 Review your estimated body fat percentage.
Understanding the Inputs
Gender
Your biological sex determines which US Navy formula is used. The male formula uses height, neck, and waist measurements. The female formula adds hip circumference because women store more fat around the hips and thighs.
How to find it: This is self reported based on biological sex. The formulas were developed using population data from US Navy personnel and are calibrated separately for male and female body composition patterns.
Why it matters: Gender selection fundamentally changes the formula and which measurements are required. Using the wrong formula would produce an inaccurate body fat estimate because male and female fat distribution patterns are significantly different.
Type: select · Default: male
Height
Your total height measured in inches. For example, someone who is 5 feet 10 inches tall would enter 70 inches (5 x 12 + 10). This is used as a reference measurement in the body fat formula.
How to find it: Stand barefoot against a wall and mark the top of your head, then measure from the floor to the mark. Alternatively, use a stadiometer at a gym or doctors office. Convert feet to inches by multiplying feet by 12 and adding remaining inches.
Why it matters: Height provides a scaling reference for the circumference measurements. The formula compares neck and waist (and hip) circumferences relative to height, so an accurate height is needed to correctly proportion the body fat estimate.
Type: number · Default: 0
Neck Circumference
The circumference of your neck measured in inches, typically just below the larynx (Adams apple). For most adults this ranges from 12-18 inches. Measure at the narrowest point, not at the base where it meets the shoulders.
How to find it: Use a flexible, non-stretchable tape measure. Stand looking straight ahead with your head held normally. Wrap the tape around your neck just below the larynx, keeping it level and snug but not compressing the skin. Measure at the end of a normal exhale.
Why it matters: Neck circumference is inversely related to body fat. A smaller neck relative to waist indicates higher body fat, while a larger neck (often with more muscle) lowers the estimated percentage. It is a surprisingly strong predictor in the Navy formula.
Type: number · Default: 0
Waist Circumference
Your waist circumference measured in inches at the level of the belly button (navel). For men this is typically 30-40 inches for healthy ranges. This is the most influential measurement in the body fat calculation.
How to find it: Stand upright and relax your stomach do not suck it in. Wrap the tape measure around your bare abdomen at the level of your navel. The tape should be snug but not tight enough to indent the skin. Measure at the end of a normal exhale for consistency.
Why it matters: Waist circumference is the strongest single predictor in the formula. It directly reflects abdominal fat, which is the most metabolically harmful type of fat. A larger waist dramatically increases your estimated body fat percentage.
Type: number · Default: 0
Hip Circumference
Your hip circumference measured in inches at the widest point of the hips and buttocks. This measurement is only required for females. For most women this ranges from 34-44 inches depending on body type and composition.
How to find it: Stand with feet together and measure around the widest part of your hips and buttocks, typically at the level of the pubic symphysis. The tape should be horizontal and snug. Wear minimal clothing or measure against bare skin for accuracy.
Why it matters: Hip circumference is included in the female formula because women store subcutaneous fat differently than men, with significant deposits around the hips and thighs. This measurement helps distinguish between lower body and abdominal fat distribution.
Type: number · Default: 0
Tips & Best Practices
- ✓ Healthy ranges: Men 10-20%, Women 18-28%. Athletes are typically lower.
- ✓ Take measurements at the same time of day for consistent tracking.
- ✓ This is an estimate. DEXA scans and hydrostatic weighing are more accurate if you need a precise measurement.
by CalculatorPro Tools · Updated 2026-07-29