Body Fat Calculator

The percentage estimates fat mass as a share of total body mass. This form infers body density from height and circumferences, then converts density to a percentage. It does not directly measure tissue, diagnose disease or determine a target percentage.

Educational estimate from the 1984 Hodgdon–Beckett circumference equations and Siri conversion. Adult military research does not establish validity for children, pregnancy or every body shape.

Measure standing height. For the male equation, measure the abdomen at the navel; for the female equation, measure the minimum waist and the widest hip/buttock circumference. Measure the neck below the larynx. Use a tape without compressing the skin, and repeat at the same landmarks. Enter the units displayed on the form.

The Hodgdon–Beckett density equations use centimeters for all lengths. Every entered inch measurement is converted by multiplying by 2.54. Weight does not enter the percentage equation. BD is predicted body density; log₁₀ is the base-10 logarithm.

Male equation: BD = 1.0324 − 0.19077 × log₁₀(abdomen − neck) + 0.15456 × log₁₀(height).

Female equation: BD = 1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height).

Siri conversion: body fat % = 495 ÷ BD − 450. All lengths in the density equations must be in centimeters.

Sources checked September 30, 2026: reproduced original male report 84-11 (1984) and Zhang et al., Journal of Thermal Biology 26 (2001), Table 1. The editorial source check is distinct from the publication dates and is not clinical review.

Zhang et al. (2001), Table 1 · Hodgdon–Beckett (1984), 84-11

The historical March 2021 Navy Guide 4, Table 2 (printed p. 15), lists 22% at height 70 inches and abdomen-minus-neck 21.5 inches. With abdomen 38 inches and neck 16.5 inches, the continuous density equation gives about 22.00%. This historical whole-percent lookup illustrates the calculation; it does not certify a current official assessment. Historical March 2021 Guide 4

The original female report was inaccessible for this source check; the female coefficients and measurement sites were checked in the 2001 table, without inferring a development cohort.

The original male Navy report 84-11 (1984), sections 2.1 and 3.3, developed its equation in 602 male Navy personnel aged 18–56 and checked it in a separate group of 100 Navy men. This military population does not establish equal performance in all adults. The female equation comes from the separate report 84-29 (1984); its exact coefficients and measurement sites are reproduced in Zhang et al. (2001), Table 1. No female sample size or age range is inferred here.

Two decimal places describe arithmetic rounding, not measurement accuracy. No clinical, athletic, acceptable or healthy category is assigned. The application rejects nonfinite results and values outside 0–75%; that is a software output bound, not a healthy range or a study eligibility criterion.

This educational form is not validated for children or pregnancy. A plausible result does not establish suitability for a body shape or medical condition. Check units and measurement sites if a result is rejected; do not change inputs to force a category.

Sources checked September 30, 2026: reproduced original male report 84-11 (1984) and Zhang et al., Journal of Thermal Biology 26 (2001), Table 1. The editorial source check is distinct from the publication dates and is not clinical review.

Zhang et al. (2001), Table 1 · Hodgdon–Beckett (1984), 84-11

Does this reproduce current official Navy assessment? No. The historical model is distinct from direct body-fat regression, BMI equations and current military policy. It does not certify compliance with current measurement or rounding rules. Consistent landmarks matter; the equation establishes no ideal time of day.

This educational form is not validated for children or pregnancy. A plausible result does not establish suitability for a body shape or medical condition. Check units and measurement sites if a result is rejected; do not change inputs to force a category.

Sources checked September 30, 2026: reproduced original male report 84-11 (1984) and Zhang et al., Journal of Thermal Biology 26 (2001), Table 1. The editorial source check is distinct from the publication dates and is not clinical review.

Zhang et al. (2001), Table 1 · Hodgdon–Beckett (1984), 84-11