Body Fat Calculator
Estimate your body fat percentage.
Understanding Body Fat Calculator
Body fat percentage is the estimated proportion of total body weight that consists of fat tissue. Unlike body weight alone, body-fat percentage provides an estimate of body composition by separating total weight into fat mass and lean body mass.
Fat is an essential component of the human body. It serves as an energy reserve, contributes to insulation and temperature regulation, protects internal organs, and participates in normal physiological processes. However, body-fat levels that are substantially above or below appropriate ranges may be associated with health concerns.
How to get a useful estimate
Body Fat Calculator is most useful when the measurements you enter are taken using the same units and definitions shown beside each field. The calculator asks for values such as Gender, Age, Height (cm), Weight (kg); enter the measurements as accurately and consistently as possible rather than rounding them before calculation.
What can change the answer
The number produced by this tool should be read in the context of the inputs and the method used by the calculator. A calculated health or fitness figure can be useful for education, planning, or tracking change over time, but it does not by itself describe every aspect of an individual’s health.
About Body Fat Calculator
Body fat percentage is the estimated proportion of total body weight that consists of fat tissue. Unlike body weight alone, body-fat percentage provides an estimate of body composition by separating total weight into fat mass and lean body mass.
Fat is an essential component of the human body. It serves as an energy reserve, contributes to insulation and temperature regulation, protects internal organs, and participates in normal physiological processes. However, body-fat levels that are substantially above or below appropriate ranges may be associated with health concerns.
Body composition varies considerably between individuals. Two people can have the same height, weight, and BMI while having different proportions of muscle and fat. This is one reason body-fat percentage can provide additional information beyond BMI.
How This Body Fat Calculator Works
This calculator uses the U.S. Navy circumference-based method to estimate body-fat percentage. The method uses body measurements rather than requiring specialized laboratory equipment.
For men, the calculation uses height, neck circumference, and abdominal or waist circumference. For women, the calculation also uses hip circumference. The equations were developed from body-composition research and provide an estimate rather than a direct measurement of body fat. also uses this U.S. Navy method as its primary body-fat calculation.
Body Fat % = 86.010 × log₁₀(Waist − Neck) − 70.041 × log₁₀(Height) + 36.76
Women
Body Fat % = 163.205 × log₁₀(Waist + Hip − Neck) − 97.684 × log₁₀(Height) − 78.387
The equations above use centimeter measurements in the metric version implemented by this calculator. The original U.S. Navy equations can also be expressed using inches; the mathematical result is equivalent after proper unit conversion.
How to Measure Your Body Correctly
Accurate measurements are important because even a small change in circumference can affect the estimated body-fat percentage. Use a flexible measuring tape and keep it horizontal and consistent when taking each measurement.
For men, the waist or abdominal measurement should be taken around the abdomen at approximately the level of the navel. The measurement should be taken without pulling the stomach inward and under normal, relaxed conditions.
The neck measurement should be taken below the larynx with the tape positioned consistently around the neck. Avoid deliberately expanding the neck or tightening the tape excessively.
For women, the hip measurement is taken around the widest horizontal circumference of the hips. The waist measurement should be taken at the appropriate waist location according to the measurement method.
• Keep the measuring tape horizontal.
• Do not pull the stomach inward.
• Do not tighten the tape excessively.
• Take measurements under similar conditions when tracking progress.
• Measuring to approximately 0.5 cm can improve consistency.
Body Fat Percentage Categories
Body-fat reference categories differ from BMI categories and are generally different for men and women. Women normally have a higher essential-fat requirement than men because of physiological and reproductive functions.
Essential Fat: 2%–5%
Athletes: 6%–13%
Fitness: 14%–17%
Average: 18%–24%
Obese: 25%+
Women
Essential Fat: 10%–13%
Athletes: 14%–20%
Fitness: 21%–24%
Average: 25%–31%
Obese: 32%+
These categories are commonly associated with the American Council on Exercise (ACE) reference classification. They are useful for general comparison but should not be interpreted as universal medical thresholds. Different body-composition methods can produce different results and reference ranges.
Essential Body Fat
Essential body fat is the minimum amount of fat required for normal physiological function. It contributes to the structure and function of cells, supports organs and tissues, and participates in important biological processes.
Extremely low body-fat levels are not automatically healthier. Attempting to maintain body fat below normal physiological requirements can have negative effects on normal bodily functions, particularly when associated with inadequate energy or nutrient intake.
Body Fat Mass and Lean Body Mass
Once body-fat percentage has been estimated, the calculator can estimate how much of the entered body weight corresponds to fat mass and how much corresponds to lean body mass.
Lean Body Mass = Body Weight − Fat Mass
Lean body mass is an estimate of everything other than fat, including muscle, bone, organs, body water, and other lean tissues. It should not be interpreted as pure muscle mass.
Body Fat and BMI
BMI and body-fat percentage measure different aspects of body composition. BMI uses only height and weight, while body-fat estimation attempts to estimate the proportion of body weight that is fat.
A person with substantial muscle mass may have a relatively high BMI while having a lower body-fat percentage. Conversely, a person can have a BMI within a conventional range while carrying a relatively high proportion of body fat.
For this reason, the calculator also provides a separate BMI-based body fat estimate. Comparing the two estimates can provide additional context, but neither calculation should be treated as a direct measurement of body composition.
Age and Body Fat
Body composition tends to change with age. Muscle mass, fat distribution, physical activity, hormonal changes, and other physiological factors can influence body-fat levels over time.
The U.S. Navy circumference equation itself does not directly use age. However, this calculator uses age when providing an additional age-based body-fat reference estimate. This allows the result to show how the calculated value compares with an age-related reference rather than implying that age is part of the Navy equation.
Ideal Body Fat by Age
The calculator provides an estimated reference body-fat percentage based on age and sex using the Jackson & Pollock reference values presented by . These values are intended as reference points rather than strict medical targets.
Age 20: Men 8.5% | Women 17.7%
Age 25: Men 10.5% | Women 18.4%
Age 30: Men 12.7% | Women 19.3%
Age 35: Men 13.7% | Women 21.5%
Age 40: Men 15.3% | Women 22.2%
Age 45: Men 16.4% | Women 22.9%
Age 50: Men 18.9% | Women 25.2%
Age 55: Men 20.9% | Women 26.3%
Estimating Weight at a Reference Body-Fat Level
If the calculated body-fat percentage is above the age-based reference value, the calculator estimates the body weight that would correspond to that reference percentage while assuming the estimated lean body mass remains unchanged.
This is a mathematical calculation, not a recommended weight-loss prescription. In real life, changes in body weight can involve changes in both fat mass and lean mass, so actual results will not necessarily follow this simplified assumption.
Accuracy of the U.S. Navy Method
The U.S. Navy method is an estimation equation rather than a direct measurement of body fat. Its result can be affected by measurement technique, body shape, fat distribution, hydration, and individual differences.
A circumference-based calculation should therefore not be interpreted as having the same precision as a controlled clinical body-composition assessment. Consistency is particularly important when using the calculator to track changes over time.
Other Methods of Measuring Body Fat
Several other methods can be used to estimate body composition. Skinfold measurements use calipers to estimate subcutaneous fat. Bioelectrical impedance analysis estimates body composition from the body's electrical properties. Hydrostatic weighing uses water displacement, while air-displacement methods estimate body volume.
Dual-energy X-ray absorptiometry (DXA) can provide a more detailed assessment of fat mass, lean tissue, and bone mineral content. However, these methods differ in cost, accessibility, equipment, and measurement assumptions, so results from different methods should not necessarily be expected to match.
Understanding Your Result
The result section displays the estimated U.S. Navy body-fat percentage, body-fat category, estimated fat mass, estimated lean body mass, BMI, BMI-based body-fat estimate, and an age-based reference value.
The calculator also shows the measurements used in the calculation so that the result can be reviewed and reproduced. This makes it easier to repeat the measurement under similar conditions when monitoring changes in body composition.
Example
Age: 30 years
Height: 175 cm
Weight: 70 kg
Neck: 40 cm
Waist: 80 cm
BMI: approximately 22.9 kg/m²
Body Fat: calculated using the U.S. Navy method
Fat Mass = Weight × Body Fat %
Lean Body Mass = Weight − Fat Mass
Important Considerations
Body-fat percentage is only one measure of body composition and should be interpreted alongside other information. The same percentage may have different implications depending on age, sex, physical activity, training status, body-fat distribution, and overall health.
Results from this calculator are estimates generated from mathematical prediction equations. They are most useful for general screening and tracking trends when measurements are taken consistently. A professional body-composition assessment may be more appropriate when a highly accurate measurement is required.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. Results are estimates and should not be considered medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for medical decisions.