Body Fat Calculator.

How the Body Fat Calculator works.

Body Fat Calculator example using the starting values.

This Body Fat Calculator example uses the starting inputs: Weight (kg): 70, Height (cm): 175, Age: 30, Sex: male.

Result: 18.13

Calculated from the entered values.

Estimated body fat %: 18.13

What the result means

Estimate body fat with the BMI/age equation. The Body Fat Calculator result describes only the measurements and method shown; it is not a diagnosis or an individualized target.

Enter a consistent scenario

Use Body Fat Calculator with values from one clearly defined scenario. The visible inputs are weight (kg), height (cm), age, sex. The BMI-and-age equation is a population estimate, not a direct body-composition measurement. Hydration, muscularity, age, sex classification, ethnicity, and measurement method can make an individual result differ. Check the unit, period, and meaning of each value before calculating; combining records from different dates can produce a precise-looking but unhelpful answer.

Follow the method

This page applies BF% = 1.20×BMI + 0.23×age − sex adjustment. The BMI-and-age equation is a population estimate, not a direct body-composition measurement. Hydration, muscularity, age, sex classification, ethnicity, and measurement method can make an individual result differ. First identify what each entered value represents, convert a percentage to the form required by the displayed formula, and retain intermediate precision. Then make a rough mental check of direction and size. Estimate body fat with the BMI/age equation. The worked result is transparent arithmetic rather than an unshown lookup.

Use the result carefully

Read the output as an answer to the narrow question described by the fields, not as a prediction of every real-world outcome. The BMI-and-age equation is a population estimate, not a direct body-composition measurement. Hydration, muscularity, age, sex classification, ethnicity, and measurement method can make an individual result differ. For Body Fat Calculator, compare results only when the measurement basis, time period, currency denomination, or grading convention is the same. This is general information, not a diagnosis, treatment target, or substitute for individual clinical care. Discuss symptoms, pregnancy dating, nutrition, exercise, or a concerning result with a qualified clinician.

Assumptions and boundaries

Before relying on Body Fat Calculator, identify what its formula—BF% = 1.20×BMI + 0.23×age − sex adjustment—holds constant and what it does not observe. The BMI-and-age equation is a population estimate, not a direct body-composition measurement. Hydration, muscularity, age, sex classification, ethnicity, and measurement method can make an individual result differ. Its entries (weight (kg), height (cm), age, sex) define the full scope of this particular result. Do not turn a rounded display into more certainty than the entered data supports; use the official record or provider documentation where it controls.

Common mistakes and next steps

For Body Fat Calculator, begin a review by comparing the displayed weight (kg), height (cm), age, sex against the source record. The BMI-and-age equation is a population estimate, not a direct body-composition measurement. Hydration, muscularity, age, sex classification, ethnicity, and measurement method can make an individual result differ. Typical mistakes are entering a percent as a decimal or vice versa, using an amount from the wrong time period, rounding before the final step, and treating an estimate as an official determination. Record the inputs and result if you need to compare scenarios later.

What the Body Fat Calculator does not include.

This Body Fat Calculator result is an estimate, not a diagnosis or treatment plan. Seek urgent care for concerning symptoms and discuss pregnancy, diet, sleep, or activity decisions with a qualified clinician.

Official context and guidance.

• CDC — About Adult BMI (opens in a new tab)