💪 Body Fat Calculator

Use this body fat calculator to estimate your body fat percentage, fat mass, lean mass, and body fat category using the U.S. Navy circumference method. Enter your sex, age, height, weight, and body measurements to see where you may fall on common body composition charts.

Body fat results

Enter your sex, age, height, weight, and body measurements above, then select Calculate Body Fat to see your estimated body fat percentage, fat mass, lean mass, and category. If you are female, be sure to include your hip circumference for the most accurate estimate.

Body composition breakdown

Once you calculate your results, this section will show a breakdown of your estimated fat mass, lean mass, and BMI based on your measurements.

Body fat calculator inputs and key terms

Understanding what each input means will help you take accurate measurements and interpret your results.

• Sex: Men and women naturally carry fat in different patterns, so the formula uses sex-specific coefficients to estimate body fat percentage.
• Age: Body composition often changes with age. While the U.S. Navy method itself does not directly use age in the formula, age is still important context when interpreting results and comparing to population norms.
• Height: Your height in inches. Used in the U.S. Navy formulas along with circumference measurements to estimate body fat.
• Weight: Your body weight in pounds. Used to convert body fat percentage into estimated fat mass and lean mass.
• Neck circumference: Measured just below the larynx (Adam’s apple), with the tape angled slightly down at the front. Keep the tape snug but not tight.
• Waist circumference: For this method, typically measured at the narrowest point of the waist or at the level of the navel (follow a consistent method each time).
• Hip circumference (women): Measured at the widest part of the hips and buttocks. This measurement is used for women in the U.S. Navy body fat formula.
• Body fat percentage: The estimated percentage of your total body weight that comes from fat tissue.
• Fat mass: Your estimated total fat in pounds (body weight × body fat percentage).
• Lean mass: Everything else besides fat—muscle, bone, organs, water, and other tissues.
• BMI (Body Mass Index): A simple ratio of weight to height (703 × weight / height² for pounds and inches). BMI does not directly measure body fat but is often used alongside body fat estimates.

Formulas used in the Body Fat Calculator

This calculator uses the U.S. Navy circumference method to estimate body fat percentage. These equations combine body size and circumference measurements to approximate body composition.

U.S. Navy body fat formulas (inches)

For men:
Body Fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76

For women:
Body Fat % = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387

where:
height, neck, waist, hip are all measured in inches, and log10 is the base-10 logarithm.

Fat mass and lean mass

Fat Mass (lb) = (Body Fat % ÷ 100) × Weight (lb)
Lean Mass (lb) = Weight (lb) − Fat Mass (lb)

Body Mass Index (BMI)

For weight in pounds and height in inches:
BMI = 703 × Weight (lb) ÷ [Height (in)]²

BMI does not distinguish between fat and muscle, so muscular individuals may have a higher BMI even when their body fat percentage is moderate. Using both BMI and body fat percentage together can give a more complete picture.

Body Fat Calculator FAQs

• How accurate is this body fat calculator?
  The U.S. Navy method is generally considered reasonably accurate for many people when measurements are taken carefully, but it’s still an estimate. Factors like body shape, tape placement, and measurement technique can affect results. Clinical methods such as DEXA scans or hydrostatic weighing are more precise but also more expensive and less accessible.
• Do I really need to measure my neck, waist, and hips?
  Yes. This method relies on circumference measurements to estimate how much of your body is likely fat versus lean tissue. For women, hip circumference is especially important. For consistent results, measure in the same spots each time and keep the tape snug but not tight.
• What is a healthy body fat percentage?
  “Healthy” can vary by sex, age, and source. In many general charts, men in the fitness or average range often fall somewhere around 10–24% body fat, while women often fall in the 18–31% range. Extremely low or very high percentages can both carry health risks. It’s best to discuss your specific situation with a healthcare or fitness professional.
• How is body fat percentage different from BMI?
  BMI is based only on height and weight, and it doesn’t distinguish between fat, muscle, and other tissues. Body fat percentage estimates how much of your body weight is fat. Someone with a high level of muscle mass may have a higher BMI but a moderate body fat percentage. Using both metrics together gives more context than either one alone.
• How often should I check my body fat percentage?
  For most people, checking every few weeks or once a month is plenty. Body fat changes more slowly than day-to-day weight. If you’re following a training or nutrition plan, tracking trends over time is more useful than focusing on small changes between single measurements.
• Can I use this calculator if I’m an athlete or very muscular?
  You can, but keep in mind that circumference-based methods and generalized body fat charts were developed for the average person. Athletes and highly muscular individuals may see estimates that are slightly higher or lower than more advanced methods. Consider using this tool as one data point alongside performance, photos, and how you feel.