Body-fat estimation methods and measurement guide

This body fat calculator provides a dedicated calculation workflow rather than a generic converter. Body-fat equations provide estimates from easy measurements. Their accuracy depends on measurement technique and how closely an individual resembles the populations used to develop the equations.

Traditional U.S. Navy circumference equation

The male equation uses waist minus neck circumference and height. The female equation uses waist plus hip minus neck and height. All measurements are converted to centimeters before applying the logarithmic formula.

BMI-based comparison

The BMI estimate uses BMI, age and the selected male or female equation term. It is shown as a comparison rather than blended with the circumference result because the two methods rely on different assumptions.

Fat mass and lean mass

Estimated fat mass equals body weight × body-fat percentage. Lean mass is the remaining body weight and includes muscle, bone, organs, water and other non-fat tissue.

How to measure consistently

Use a flexible tape held level and snug without compressing the skin. Repeat at the same anatomical location and similar time of day; small circumference differences can change the estimate.

Why methods disagree

Hydration, fat distribution, muscularity, age and measurement error can affect the equations differently. A consistent trend from the same method can be more useful than comparing unrelated methods.