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Body Fat Calculator

Use this body fat calculator to estimate body fat percentage from height, weight, neck, waist, and hip measurements in pounds/inches or kilograms/centimeters.

Method and assumptions documentedPlanning estimateSource note includedNo expert review claimed

Live calculator

Body fat estimate

Estimated body fat32.9%

U.S. Navy circumference-style estimate from tape measurements.

Fat mass54.3 lb

110.7 lb estimated lean mass.

Measurement value59 in

Formula still uses the converted 66 in / 167.6 cm height and in/lb inputs.

Estimate note

Tape-measure formulas can move a lot when measurements change by even a small amount. Use consistent measurement points and treat the result as a tracking estimate, not a clinical body composition test.

Use this as a planning estimate, not medical advice. Medical conditions, medication, pregnancy, eating disorder history, or disease-specific nutrition needs should be handled with a qualified professional.

Quick answer

Body Fat Calculator: what it calculates

Body Fat Calculator calculates estimated body fat from sex, weight, height, neck, waist, hip, and 1 additional input. The visible formula is Men: 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76; women: 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387.

ResultEstimated body fat
InputsSex, Weight, Height, Neck, Waist, Hip, Unit system
FormulaU.S. Navy-style circumference formula

Formula

U.S. Navy-style circumference formula

Men: 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76; women: 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387

The equation uses inches internally. Metric inputs are converted to inches before calculation, and tape estimates remain sensitive to measurement technique.

How to use

Steps

  1. Choose pounds with inches or kilograms with centimeters.
  2. Choose sex.
  3. Enter weight and height.
  4. Enter neck and waist measurements.
  5. Enter hip measurement when using the female formula.

Example

Sample calculation

ProfileFemale, 5 ft 6 in / 167.6 cm
Measurements13 in neck, 32 in waist, 40 in hips / 33, 81.3, 101.6 cm
EstimateAbout 33% body fat

Calculator use

Best for

  • Use this body fat calculator to estimate body fat percentage from height, weight, neck, waist, and hip measurements in pounds/inches or kilograms/centimeters.
  • Estimating body, hydration, protein, calorie, macro, or fitness planning numbers with assumptions visible.
  • Comparing rough scenarios before tracking trends or discussing the result with a qualified professional.
  • Keeping formula inputs visible so the number can be checked later instead of treated as a diagnosis.

Before relying on it

Check first

  • Treating a screening or planning estimate as medical, nutrition, eating-disorder, pregnancy, or disease-specific advice.
  • Ignoring age, sex, medication, body composition, training status, medical history, heat, illness, or measurement method.
  • Changing diet, hydration, or training aggressively from one calculator result without appropriate context.

Details

What to know before using the result

Measurement qualityTape placement matters

Small tape-measure differences can shift the result, so use consistent landmarks, the same unit system, and a non-stretch tape.

Estimate typeCircumference method

This is not the same as DEXA, hydrostatic weighing, or a clinical body composition assessment.

Tracking useCompare like with like

The result is most useful when you measure the same way over time rather than treating one estimate as exact.

Source notes

References used for this calculator

U.S. NavyPublishes body composition assessment guidance with circumference-based body fat estimation tables.Centers for Disease Control and PreventionNotes that BMI does not directly measure body fat, which is why body composition estimates need separate interpretation.National Institute of Standards and TechnologyPublishes common inch, centimeter, pound, and kilogram conversion factors used for unit switching.

Benchmarks

How to read the result

Tape method: Convenient estimate.

Easy to repeat at home, but less precise than clinical body composition tests.

DEXA or clinical testing: More direct.

May be useful when accuracy matters for medical or athletic decisions.

Trend over time: More useful than one reading.

Consistent repeated measurements are usually more useful than a single estimate.

Calculator accuracy

Methodology and assumptions

Formula

Men: 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76; women: 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387

Inputs used

Sex, Weight, Height, Neck, Waist, Hip, Unit system

Limitations

Health results are screening or planning estimates. Age, body composition, medication, medical history, pregnancy, and professional guidance can change the right interpretation.

Review record

Method and sources checked on July 12, 2026. The documented method, source timing, validity conditions, and reliance limits were checked on this date.

Method provenanceEstimate · toolkitshelf.body-fat-circumference.v1
Maintained by
Toolkit Shelf
Calculation class
Estimate
Method version
toolkitshelf.body-fat-circumference.v1
Source date
June 28, 2013
Source checked
July 12, 2026
Intended audience
Adults using repeatable height, neck, waist, and where applicable hip measurements for a tape-based body-fat trend estimate.
Valid when
Use consistent anatomical landmarks, posture, breathing, and tape tension. Implausible or nonpositive circumference differences are invalid; the displayed estimate is bounded to 2% through 75% for interface safety.
Reliance boundary
This is a circumference-based estimate, not a clinical body-composition measurement, diagnosis, service-eligibility decision, or substitute for professional assessment.
Data freshness
The exact published circumference equations were checked on July 12, 2026. The calculator preserves those inch-based equations after visible unit conversion and does not assert current service policy.
Cite this page

Toolkit Shelf. Body Fat Calculator. https://toolkitshelf.com/tools/body-fat-calculator

FAQ

Common questions

How does the body fat calculator work?

It applies a U.S. Navy-style circumference equation using height and tape measurements from the neck, waist, and hips. Metric inputs are converted to inches for the formula.

Is the body fat result exact?

No. Tape-based body fat is an estimate and can change with measurement technique, hydration, posture, and body shape.

Why does hip measurement appear only for female input?

The common U.S. Navy-style female equation uses waist, hip, neck, and height, while the male equation uses waist, neck, and height.

When should I ask a clinician?

Ask a clinician or qualified nutrition professional when pregnancy, medication, medical history, eating disorder risk, symptoms, or disease-specific guidance matters.

Why can health formulas be misleading?

Health formulas simplify age, sex, body composition, training status, measurement method, pregnancy, and medical context into a planning estimate.

Is this medical advice?

No. Health calculators are screening or planning tools and do not diagnose, treat, or replace professional medical or nutrition guidance.