🩺 Body Fat Calculator: US Navy Method Body Fat Percentage

Estimate your body fat percentage using the US Navy method. Enter your height, neck, waist, and hip measurements for instant, private results.

Last updated: 18 October 2026

Body Fat Calculator: US Navy Method Body Fat Percentage

Estimate your body fat percentage from four tape measurements using the US Navy circumference method. Enter height, neck, and waist (plus hip for women); optionally add weight to split fat mass and lean mass. The page runs entirely in your browser and does not store your measurements.

What this is. A rough circumference-based estimator for adults who want to track relative change without lab equipment. What this is not. A diagnosis, a medical device, or a substitute for DEXA or other laboratory methods. Not medical advice. Not for under-18 users, pregnancy, or treatment decisions.

Body fat percentage calculator

Choose units, sex, and measurements. Results update as you type. Metric entries are converted to inches exactly (divided by 2.54) before the Navy formulas run.

Unit system

US (in / lb) Metric (cm / kg)

Sex (required for the Navy formulas)

Male Female

Height (in)

Standing straight, no shoes. Inches for US units; centimeters for metric.

Neck circumference (in)

Measure below the larynx (Adam's apple), on bare skin, head level, tape snug but not tight.

Waist circumference (in)

At the navel for men.

Weight (lb) (optional — enables fat and lean mass)

Enter weight only if you want fat mass and lean mass. Leave empty to see percentage alone.

How to calculate body fat percentage with a tape measure

This page implements the US Navy circumference method, a set of published equations that estimate body fat percentage from height, neck, waist and (for women) hip girth. The Navy and Department of Defense have used circumference-based screening as a field method when densitometry is unavailable. The same idea appears under the name body fat percentage calculator in many fitness tools, but not every online calculator uses the same coefficients or measurement sites — mixing an older male formula with a newer female formula is a common source of disagreement between sites.

The arithmetic is simple once the inputs are in inches:

Male: body fat % = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Female: body fat % = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

Metric users enter centimeters; each value is divided by 2.54 exactly before the logarithm so metric and US inputs describe the same body. The calculator refuses to print a number when the logarithm argument would be zero or negative (for example waist equal to neck, or neck larger than waist + hip).

Rule status (2026-10-18). The formulas above are treated as candidate coefficients carried from the product brief, the branch is marked Before production reliance, re-open the current official Navy body-composition publication and the category table and update Rules data in script.js.

Measurement guide: how to take neck, waist and hip correctly

Technique matters as much as the formula. Use a flexible cloth tape, measure on bare skin, keep the tape level, and do not pull it tight enough to compress flesh. Breathe out normally before reading the waist. For best tracking, measure at the same time of day, after similar meals, and use the same landmarks each session.

Measurement sites at a glance

Neck — below the larynx, head level

snug

Waist (men) — at the navel

level

Waist (women) — narrowest point above the navel

level

Hip (women) — widest point of the buttocks

level

Measure the neck with the head slightly raised, tape under the larynx on the bare skin.
Men: find the navel, wrap the tape around the abdomen at that height, relax the stomach.
Women: for the waist use the narrowest torso point above the navel; for the hip stand with feet together at the widest buttock point.
Do not use pants size as a substitute; clothing ease distorts the circumference.
Enter the same unit system you measured in, or let the converter handle the difference — both paths should agree.

Worked examples (hypothetical inputs)

These examples use the same candidate Navy coefficients the page runs. They are labeled hypothetical so you can check the arithmetic, not to describe real people.

Worked examples: inputs, formula path, and displayed result
Example	Sex	Height	Neck	Waist	Hip	Key intermediate	Body fat (unrounded)	Shown
A — baseline male	Male	70 in	15 in	34 in	—	waist − neck = 19 in	17.513085%	17.5%
B — baseline female	Female	65 in	13 in	30 in	38 in	waist + hip − neck = 55 in	28.556264%	28.6%
C — metric equals US	Male	177.8 cm	38.1 cm	86.36 cm	—	each ÷ 2.54 → same inches as A	17.513085%	17.5%
D — one inch smaller waist	Male	70 in	15 in	33 in	—	waist − neck = 18 in	15.493476%	15.5%
E — mass split at 180 lb	Male	70 in	15 in	34 in	—	fat = 180 × 17.513085%	fat 31.52 lb · lean 148.48 lb	31.5 / 148.5 lb

Examples D and E illustrate two product decisions: a one-inch waist difference moves the example male result by about two percentage points, and the fat/lean split uses the unrounded percentage before display rounding. Invalid pairs (waist equal to neck, neck larger than waist + hip) never produce a percentage; the panel shows a plain-language message instead.

Comparison: where circumference estimates fit among body fat methods

People often ask how to know your body fat percentage without a clinic visit. The table below compares the approach this page uses with other common methods on the dimensions that matter for home tracking: equipment, effort, and how closely the reading tracks laboratory reference methods. No figure here is a guaranteed error band; laboratory comparisons vary by study and population.

Body fat methods compared for home use
Method	What you need	Best for	Main trade-off	Used on this page
US Navy circumference (this tool)	Cloth tape, scale optional	Tracking change with almost no cost	Body shape and tape skill affect the number; not a diagnosis	Yes
Skinfold calipers	Calipers plus practice	Sites you can pinch consistently	Technician skill and site selection dominate error	No — out of scope
Bioimpedance scales / bands	Device with electrodes	Quick repeated readings under similar conditions	Hydration and meal timing swing results	No — out of scope
DEXA (laboratory)	Clinic appointment	Reference measurement and regional fat	Cost, access, and it is still an estimate model	No — out of scope
BodPod / hydrostatic weighing	Specialized facility	Density-based reference points	Limited locations and scheduling	No — out of scope

What moves a circumference result most (using the baseline male example)
Change in input	Body fat % (candidate formula)	Difference vs baseline	Practical reading
Baseline: waist 34 in, neck 15 in	17.5%	—	Reference case A
Waist 33 in (−1 in)	15.5%	−2.0 points	Tape placement can mimic a real change
Waist 35 in (+1 in)	19.4%	+1.9 points	Large enough to hide real week-to-week noise
Neck 16 in (+1 in), waist unchanged	15.5%	−2.0 points	Neck accuracy matters; do not stretch the tape

Sensitivity values in the second table are computed live in the calculator panel for your own inputs; the table shows the baseline case so the pattern is obvious before you type.

Infographic: how a one-inch waist change shifts the estimate

Using the same hypothetical male as the worked examples (height 70 in, neck 15 in), the chart below shows body fat percentage for waist sizes from 31 to 37 inches under the candidate Navy formula. The point of the picture is slope, not any single bar: small waist changes produce visible percentage jumps.

Male example: body fat % vs waist circumference (height 70 in, neck 15 in)

Waist 31 in (waist − neck = 16)

11.1%

Waist 32 in

13.4%

Waist 33 in

15.5%

Waist 34 in (worked example A)

17.5%

Waist 35 in

19.4%

Waist 36 in

21.3%

Waist 37 in

23.0%

Bars are scaled against a 25% reference width for readability. Exact values shown next to each bar.

Common mistakes and key conditions

What to do

Measure on bare skin with a flexible tape; keep the tape level all the way around.
Use the published landmarks (neck under the larynx; waist at the navel for men; hip at the widest buttock point for women).
Compare like with like: same tape, same time of day, similar hydration and training status.
Track a trend over several weeks rather than reacting to a single morning.
Enter weight only when you want the fat/lean mass split; percentage alone does not require it.

What to avoid

Pulling the tape tight “to be sure” — compression changes the circumference and the formula.
Using waist sizes printed on jeans, or measuring over a thick shirt.
Expecting the number to match a DEXA printout or a clinic bioimpedance machine.
Treating the estimate as medical advice, a diagnosis, or a reason to change medication or diet abruptly.
Switching between male and female formulas, or between different published coefficient sets, to chase a preferred number.

Invalid combinations are blocked on purpose. If waist equals neck (male), the log argument becomes zero; if neck exceeds waist + hip (female) or waist (male), the argument is negative. In those cases the panel shows More information required with a plain-language fix instead of NaN, Infinity, or a made-up percentage.

FAQ

How do you calculate body fat percentage at home?

Measure height, neck, waist and (for women) hip with a cloth tape, enter sex and units, and let this calculator apply the US Navy circumference equations. Those equations take base-10 logarithms of the girth combinations and of height, all in inches. Home measurements work best when you keep landmarks, tension and time of day consistent from session to session.

What is a healthy body fat percentage?

Healthy ranges are usually published as sex- and age-banded category tables (for example tables used by fitness organizations such as the American Council on Exercise). If you open a body fat percentage chart on another site, check whether it states the source study or agency and the age bands it uses — many charts mix outdated bands. Use the percentage to watch your own trend over weeks, and discuss personal targets with a qualified clinician if health decisions depend on them.

What is a healthy body fat percentage for women?

Women typically carry a higher essential-fat fraction than men, and published bands shift with age. Because the category source was not verified here, no numeric female band is stated as official on this page. Track change with the same circumference method, the same landmarks, and similar conditions.

How accurate is the Navy body fat calculator?

Circumference methods are screening tools. Published comparisons with densitometry and similar laboratory references show disagreement that depends on body shape, sex, and how carefully the tape is placed — small tape errors can move the percentage by one or two points, and larger technique errors can move it more. Treat the output as an estimate for personal tracking, not a medical measurement or a promise of lab-grade accuracy.

Why do neck and waist measurements matter so much?

Both girths sit inside the logarithm of the formula. For the male example (height 70 in, neck 15 in, waist 34 in), changing only the waist by one inch shifts the estimate by about two percentage points. That is why a rolled tape or a different waist landmark can look like sudden progress or sudden setback.

How to calculate body fat percentage if I only have metric measurements?

Switch the unit system to metric, enter centimeters and kilograms, and continue. Each length is divided by 2.54 before the logarithm, so the same body in inches and centimeters produces the same percentage (see worked example C). Weight in kilograms is converted only for the optional fat/lean mass display.

How to know your body fat percentage without a gym InBody scan?

A tape measure and a consistent routine are enough for this method. Write down each session’s waist, neck, hip and weight, compute the percentage here, and compare multi-week averages instead of single readings. If you later obtain a DEXA or clinic bioimpedance result, keep the lab value separate — do not force the two scales to match.

Glossary

Body fat percentage: Body fat mass expressed as a percentage of total body weight.
Lean mass: Everything that is not fat mass in this simple split (muscle, bone, organs, water). Not identical to “muscle mass.”
Fat mass: Estimated fat weight, here = body weight × body fat percentage (from the unrounded percentage).
US Navy circumference method: A family of log-based equations that estimate body fat from height and selected girths, developed for field screening when laboratory methods are unavailable.
log₁₀: Base-10 logarithm, as used in the candidate coefficients on this page.
DEXA: Dual-energy X-ray absorptiometry, a clinic reference method that models fat and lean compartments; still an estimate model, not a direct weighing of every tissue.
More information required: The state this page shows when inputs are empty, out of range, or would make a logarithm undefined — no percentage is invented.
Estimate with limitations: Status used for results that are calculable but inherently approximate (circumference screening, optional mass split).

Method & sources

Product: Body Fat Calculator (US Navy circumference method)
Market: United States · en-US · USD
Rule version: Loaded from rules data
: 2026-10-18 — machine research stage found no opened primary source in this run
Branch status: Estimate with limitations
Calculation location: All arithmetic runs in your browser; measurements are not uploaded or saved by this page.

Candidate authorities to re-open before treating any number as official

These are official starting points, not pages opened and verified:

US Department of Defense / US Navy body-composition and circumference-method publications — start at https://www.defense.gov and Navy personnel-research pages; record the exact document URL when re-verified.
American Council on Exercise (ACE) body fat percentage categories — start at https://www.acefitness.org; category scale stays hidden until that table is opened and cited.
Peer-reviewed comparisons of circumference methods against DEXA or densitometry for a quoted error range.

Formulas currently in the engine (candidate coefficients)

Male: 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Female: 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

Byline: Varnda Editorial Team. Corrections: use the feedback channel on varnda.com if available on the live site — no email address is invented here.

Limitations, exclusions and assumptions

Not medical advice. Nothing here diagnoses, treats, or recommends care. Speak with a licensed clinician before changing diet, training, or medication based on a body-fat estimate.
Scope. Adult users only; minors, pregnancy, and clinical edema or unusual body compositions are outside the supported scope.
Method family. Only the Navy circumference equations are implemented. Skinfold, bioimpedance, DEXA, and visual methods are out of scope.
Verification. Treat every regulated or sourced number as editable configuration with a default, not as official fact.
Rounding. Internal computation uses full double precision; body fat percentage displays to one decimal (half-up). Fat and lean mass use the unrounded percentage and display to one decimal in the selected mass unit.
Mass split. Fat mass = weight × percentage; lean mass = weight − fat mass. This ignores bone density nuances that laboratory methods model.
Privacy. No account, no analytics of measurements, no server calls for the calculation. Optional local storage, if used, stores only non-sensitive form defaults on your device.

Bottom line

Enter height, neck, waist and (for women) hip; add weight only if you want a fat/lean split. You get a body fat percentage from the Navy circumference equations, a sensitivity view for one-inch waist changes, and a clear blocked state when the math is undefined. Use it to follow your own trend with honest limits — not as a lab result, and not as medical advice. Re-verify the coefficients and any category table against the official publications listed above before relying on absolute values.

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Body Fat Calculator: US Navy Method Body Fat Percentage

🩺 Body Fat Calculator: US Navy Method Body Fat Percentage