Body fat calculator: Navy, Army and BMI methods
The body fat calculator defaults to the US Navy tape estimate and compares CUN-BAE and Deurenberg, which use BMI, age and sex. Fat-free mass equals weight × (1 − body fat/100). These are estimates with errors of several percentage points. The Army now uses waist-to-height ratio, a separate measure rather than body-fat percentage.
Values recalculate as you type. No measurements are sent or stored: the math runs in your browser.
Error and scope: Hodgdon’s own summary reports standard errors of 3.52 percentage points for men and 3.72 for women for the historical Navy equations. These are not guaranteed individual limits or home-measurement accuracy. CUN-BAE reports 4.66 and Deurenberg 4.1 percentage points; the results should not be averaged.
General information, not diagnosis or medical advice. These percentages are not eating or weight targets. If the numbers cause distress, you can leave the calculator and talk with a professional; do not change habits or medication because of this result.
How the calculation works
For Navy, H, N, A, W and P are inches: height, neck, abdomen at the navel, natural waist and hip. Every cm input is divided by 2.54; log₁₀ is the base-ten logarithm.
Navy, male: % = 86.010 × log₁₀(A − N) − 70.041 × log₁₀(H) + 36.76
Navy, female: % = 163.205 × log₁₀(W + P − N) − 97.684 × log₁₀(H) − 78.387
Deurenberg: % = 1.20 × BMI + 0.23 × age − 10.8 × S − 5.4; S = 1 male, 0 female.
CUN-BAE: % = −44.988 + 0.503 × age + 10.689 × F + 3.172 × BMI − 0.026 × BMI² + 0.181 × BMI × F − 0.02 × BMI × age − 0.005 × BMI² × F + 0.00021 × BMI² × age; F = 0 male, 1 female.
BMI = weight (kg) ÷ height (m)²; age is years. Fat-free mass (kg) = weight (kg) × (1 − body-fat percentage/100).
Sources: Potter et al. 2022 reproduces Hodgdon and Beckett’s 1984 equations; original reports 84-11 and 84-29 were unavailable to read. Potter prints the female term as abdomen minus neck. This calculator uses waist + hip − neck following the female measurement protocol in AR 600-9 and explicitly discloses that documentary discrepancy. Hodgdon’s own chapter supplies the historical errors; it is not a new validation of this calculator.
Deurenberg et al. 1991 prints its equation and error in the abstract. Gómez-Ambrosi et al. 2012 is the original CUN-BAE reference; coefficients and sex coding were checked on SEEDO’s tool. CUN-BAE was developed in adults aged 18–80 with BMI 12.4–72.8 and studied primarily in white participants; equal validity across all populations is not assumed.
Limits of the estimate
Tape position, tension and repeatability change the reading; measure without compressing skin, keeping the tape level after a normal exhale. Measurements are not rounded before calculation, and the tool does not reproduce an official military assessment protocol. BMI methods cannot distinguish muscle from fat. Fat-free mass includes bones, organs and water; it is not muscle mass.
The tool is not for children, pregnancy, breastfeeding, amputations or severe edema. Negative results and values above 100% are not clamped to look plausible. CUN-BAE and Deurenberg are hidden outside their sample limits; a value within those limits still does not guarantee individual validity. Seek professional assessment when body composition matters clinically.
Published error and what it means
| Method | Error (body-fat percentage points) | Context |
|---|---|---|
| Navy | 3.52 / 3.72 | Men / women; Hodgdon’s historical summary |
| Deurenberg | 4.1 | Adult standard error of estimate |
| CUN-BAE | 4.66 | Published standard error of estimate |
Army and Navy: military standards, not health targets
Checked September 7, 2026: the Army’s official summary of Directive 2026-13 establishes waist-to-height ratio as its sole assessment, with a standard below 0.55. Previous body-fat methods and height-weight screening tables were rescinded. The Army result is therefore a separate ratio, not a fat estimate or a fitness verdict.
WHtR = waist at navel (cm) ÷ height (cm). The ratio is dimensionless and displayed to three decimal places.
This historical Navy estimate does not establish compliance with the current Navy assessment. Current limits could not be verified from an accessible Navy source, so no maximum percentages or waist screening thresholds are published. For service decisions, consult your unit’s official procedure. Military employment standards are not health recommendations for the public.
Body-fat ranges: a limited reference
The press item hosted by ACE quotes 18–24% for men and 25–31% for women as average nonathlete ranges. This is descriptive guidance from a private organization, not a diagnostic band or target. The complete five-category table could not be verified and is not reconstructed here.
| Description | Male body fat (%) | Female body fat (%) |
|---|---|---|
| Average nonathlete | 18–24 | 25–31 |
Frequently asked questions
How does the US Navy body fat calculator work?
The US Navy method estimates fat from height and circumferences: abdomen and neck for the male equation, and natural waist, hip and neck for the female equation. It uses base-ten logarithms with inches, converted from cm where needed. This historical prediction is not a direct measurement or a current official military assessment.
What is the Navy method’s error margin?
Hodgdon’s own summary reported historical standard errors of 3.52 percentage points for men and 3.72 for women. Those figures describe fit in studied samples, not guaranteed limits around your result. Tape placement and individual differences add uncertainty. This page distinguishes the published statistical errors from any promise of accuracy for a particular person.
What is CUN-BAE and how does it differ from BMI?
CUN-BAE is the Clínica Universidad de Navarra Body Adiposity Estimator. It combines BMI, age and sex in an equation published by Gómez-Ambrosi and colleagues; SEEDO reproduces its coefficients. It predicts body-fat percentage, while BMI simply relates weight to height. It remains a population estimate and cannot directly separate muscle from fat.
Does the Army still use body-fat percentage in 2026?
The Army’s official summary of Directive 2026-13 states that waist-to-height ratio is its sole body composition assessment and rescinds previous body-fat methods. The published standard is a ratio below 0.55. This calculator shows the ratio as a mathematical reference; it does not certify the result of an official assessment or service eligibility.
Is fat-free mass the same as muscle mass?
No. Fat-free mass includes muscle along with water, organs, bones and other tissues. Here it is calculated as weight multiplied by one minus body-fat percentage divided by one hundred. It inherits the uncertainty of the selected method and cannot determine how much muscle someone has or how much they should gain.
What body-fat percentage is healthy?
No single percentage describes everyone’s health. Age, sex, measurement method and clinical context affect interpretation. The verified ACE fragment gives average nonathlete ranges of 18–24% for men and 25–31% for women; these are not diagnoses or personal goals. Consult a professional when you need an individual assessment rather than a general descriptive reference.
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