Body Fat Calculator
Estimate your body fat percentage using height and circumference measurements, with optional fat-mass and lean-mass calculations from your body weight.
Measurements Used
What Is Body Fat Percentage?
Body fat percentage describes the estimated proportion of total body weight that consists of fat tissue.
It is different from body weight alone. Two people can weigh the same amount while having different proportions of fat, muscle, bone, water, and other tissues.
A body fat calculator can provide a useful estimate for tracking purposes, but the number should not be treated as a direct measurement of your body composition.
How Does This Body Fat Calculator Work?
This calculator uses a circumference-based prediction method commonly associated with the Hodgdon body-composition equations.
The male and female equations use different combinations of circumference measurements.
Men
Women
These versions of the equations use measurements in inches. If you enter centimeters, the calculator converts the measurements to inches internally before performing the calculation.
How to Take Your Measurements
Measurement technique can have a major effect on the calculation, so try to measure consistently each time.
Height
Stand upright without shoes and use your normal standing height.
Neck
Measure around the neck just below the larynx while looking straight ahead and keeping the shoulders relaxed.
Male Abdomen
For men, measure horizontally around the abdomen at the level of the navel after a normal relaxed exhalation.
Female Waist
For women, measure the natural waist at the point of minimal abdominal circumference.
Female Hips
Measure around the hips at the greatest protrusion of the buttocks, keeping the tape approximately level.
Repeat if Needed
If a measurement seems unusual, repeat it rather than relying on a single rushed reading.
Body Fat Calculation Example for a Man
Consider a man who is 70 inches tall with a 36-inch abdominal circumference and a 15-inch neck circumference.
36 − 15 = 21 inches
Step 2 — Apply the equation86.010 × log₁₀(21) − 70.041 × log₁₀(70) + 36.76
Body Fat Percentage vs. BMI
Body Fat Percentage
Attempts to estimate the proportion of total body weight represented by fat tissue.
Body Mass Index
Compares total body weight with height but does not directly estimate how much of that weight is fat.
How Are Fat Mass and Non-Fat Mass Calculated?
Once the calculator has estimated body fat percentage, your body weight can be used to derive an estimated amount of fat mass.
The second value includes much more than skeletal muscle. It also includes body water, bones, organs, connective tissues, and other non-fat components.
Is Non-Fat Mass the Same as Muscle Mass?
No. Subtracting estimated fat mass from total body weight gives a broad non-fat or fat-free mass estimate.
Skeletal muscle is only one part of that value. Water, bone, organs, connective tissue, and other tissues also contribute to body weight that is not fat.
A circumference calculator therefore cannot tell you exactly how many kilograms or pounds of skeletal muscle you have.
Body Composition After Age 50
Body composition can change with age even when scale weight remains relatively stable.
For example, changes in muscle and fat can partly offset one another on the scale. This means body weight alone may not show the full picture.
For adults over 50, body composition can be considered alongside strength, mobility, physical activity, waist measurements, nutrition, blood pressure, laboratory results, and other health information.
Why Doesn't This Calculator Label Your Body Fat as “Good” or “Bad”?
Body fat reference ranges can vary according to the organization, population, sex, age, measurement method, and purpose of the assessment.
A military body-composition standard, athletic reference, clinical assessment, and general population reference may not use the same cutoffs.
For that reason, this calculator focuses on estimating body fat percentage rather than assigning a universal health category that may not be appropriate for every user.
Limitations of Circumference-Based Body Fat Calculators
- They are prediction equations: the result is an estimate rather than a direct measurement.
- Measurement technique matters: a slightly different tape position can change the result.
- Body proportions vary: people with similar circumferences may still have different body composition.
- The equations were developed from population data: an equation cannot perfectly predict every individual.
- Fat distribution is simplified: a few circumference measurements cannot capture all differences in where fat is stored.
- Clinical methods may disagree: DXA, bioelectrical impedance, skinfold measurements, air-displacement methods, and circumference equations can produce different estimates.
Other Ways Body Composition Can Be Estimated
DXA
Dual-energy X-ray absorptiometry can estimate fat, lean tissue, and bone composition using specialized equipment.
Bioelectrical Impedance
BIA devices estimate body composition from electrical impedance and are found in many consumer and professional body-composition scales.
Skinfold Measurements
Skinfold calipers measure subcutaneous tissue at selected sites and use prediction equations to estimate body fat.
Circumference Equations
Tape measurements are inexpensive and accessible but rely heavily on consistent measurement technique.
Using Body Fat Estimates to Track Progress
If you use circumference measurements repeatedly, try to measure under similar conditions each time.
Use the Same Tape
Using the same measuring tape can help improve consistency.
Use the Same Locations
Keep the tape at the same anatomical measurement sites each time.
Measure Consistently
Try to use similar conditions and a relaxed posture for repeated measurements.
Focus on Trends
Repeated measurements may be more useful for tracking a trend than focusing heavily on one isolated result.
Frequently Asked Questions
It uses sex-specific circumference equations based on height and measurements of the neck and torso. Women also enter hip circumference.
Not in the circumference equation used here. Body weight is collected so the calculator can convert the estimated percentage into estimated fat mass and non-fat mass.
No. A circumference formula predicts body fat from tape measurements. DXA uses specialized imaging technology and can produce different results.
For the male equation used by this calculator, measure the abdomen horizontally at approximately the level of the navel after a normal relaxed exhalation.
Measure the natural waist at the smallest abdominal circumference and the hips around the greatest protrusion of the buttocks.
Circumference measurements are direct inputs to the prediction equation. Changing the tape position or circumference therefore changes the estimated body fat.
No. BMI compares weight with height, whereas body fat percentage attempts to estimate the proportion of body weight represented by fat tissue.
No. Non-fat mass includes muscle but also includes water, bone, organs, connective tissue, and other non-fat components.
Age is not a direct input to the Hodgdon circumference equations used by this calculator. Body composition can still change substantially with age.
