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Calculate your body fat percentage using BMI and waist circumference formulas. Get instant body composition insights for fitness and health management.
Enter body data to start calculation
Overview
Understand what the tool solves, how it works, and the boundaries of its data.
This calculator estimates body-fat percentage from height, weight, age, and a male/female formula setting. It first computes body mass index (BMI), which is weight divided by height squared, then applies an adult prediction equation. The displayed outputs are BMI, estimated body-fat percentage, and a preset category label. It does not use a tape measure, skinfold calipers, or a body-composition scan.
BMI = weight in kg ÷ height in meters²
Estimated body fat (%) = 1.2 × BMI + 0.23 × age − 5.4 − 10.8 × S
S = 1 for the male setting and S = 0 for the female setting.
The equation comes from a published adult population study relating BMI to body-fat percentage while accounting for age and sex. An estimate produced by a population equation is not a direct reading of an individual’s fat mass. The page rounds BMI and body-fat percentage to one decimal place; negative formula results are displayed as zero.
The result card assigns a label using fixed percentage bands selected by the tool. Those bands are part of the display logic, not a diagnosis, a personalized target, or a clinical finding. Labels such as “athlete” or “fitness” do not establish training status. Keep the numerical estimate and its method visible when sharing a result so that the category is not mistaken for a measured fact.
For example, a 30-year-old male input at 175 cm and 75 kg gives BMI about 24.5. Applying the displayed equation gives an estimated body-fat percentage of about 20.1%. The number describes the equation’s output for those inputs, not a laboratory measurement.
Guide
Follow the workflow and verify inputs and outputs with practical examples.
Select metric for centimeters and kilograms, or U.S. customary inputs for feet, inches, and pounds. In customary mode, enter height across the feet and inches fields and weight in pounds.
Provide age in years and select the male or female setting used by the equation. The equation requires both values as well as height and weight.
The result updates when valid inputs are present. Review BMI and estimated body-fat percentage together, then treat the category as the page’s preset label rather than a health conclusion.
If you repeat an estimate later, keep the method and unit interpretation consistent. Record the inputs with the result so a later comparison is not confused with a change in measurement method.
Use cases
See how the tool fits into real work and everyday tasks.
A person tracking routine measurements can enter the same height, weight, age, and formula setting over time. The estimate can be logged alongside the date, while recognizing that a BMI-based equation may not track body composition precisely for one person.
A coach or student can vary one input to see how age, height, weight, or the formula setting changes the calculated result. This is useful for understanding the equation, not for diagnosing a condition or prescribing a target.
Q&A
Find concise answers to common questions and confusing cases.
No. It predicts a percentage from BMI, age, and the selected formula setting. It does not measure fat tissue or body-fat mass directly.
Calculators may use different equations or add circumference, skinfold, or other measurements. This page uses only the BMI-based equation shown above, so compare results only when the methods match.
No. They are preset labels attached to fixed percentage bands in the tool. The labels do not diagnose health or establish an individual’s appropriate body-fat level.
BMI is an input to the estimate and is also returned as a separate value. It is a weight-to-height index, not a direct measure of body fat; the CDC describes BMI as a screening measure.
Notes
Review scope, result limitations, and important precautions before use.
This estimate is not a medical diagnosis or a substitute for assessment by a qualified health professional.
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