What This Calculator Estimates
Body fat percentage describes fat mass as a proportion of total body weight. This calculator does not directly measure fat tissue. It applies a circumference equation to height, neck, waist, and—for women in this equation—hip measurements to produce an estimate.
The result can add context that weight alone cannot provide, but it still has prediction error. Body shape, muscularity, age, population differences, tape tension, and landmark placement can all affect how closely the estimate matches a laboratory method.
How the Classic U.S. Navy-Style Equation Works
The equation commonly known online as the U.S. Navy body fat method uses logarithms of circumference differences relative to height. This calculator converts imperial inputs to centimeters before applying the coefficients below.
Calculator equations
Men
495 ÷ [1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)] − 450
Women
495 ÷ [1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.221 × log₁₀(height)] − 450
All formula inputs are centimeters. The current official U.S. Navy body-composition program uses updated procedures, so this consumer calculator should not be used to predict an official service assessment.
How to Read Your Body Fat Result
Start with the estimated percentage, then use the reference band only as broad fitness context. The band is not an age-adjusted medical cutoff or a recommended target. If you entered body weight, the calculator also converts the percentage into estimated fat mass and fat-free mass.
Body fat estimate
The percentage predicted from the selected equation and your tape measurements.
Reference band
A descriptive fitness range for context—not a diagnosis, score, or universal goal.
Mass estimates
Fat mass and fat-free mass are shown only when you provide body weight.
Body Fat Calculation Examples
These examples show how the calculator reports the classic circumference estimate. Small measurement differences can change the result, so they are demonstrations rather than comparison targets.
| Example inputs | Estimate | With body weight |
|---|---|---|
| Male · 175 cm height · 37 cm neck · 82 cm waist | 15.4% | At 75 kg: about 11.5 kg fat mass and 63.5 kg fat-free mass |
| Female · 165 cm height · 32 cm neck · 72 cm waist · 96 cm hip | 26.4% | At 60 kg: about 15.8 kg fat mass and 44.2 kg fat-free mass |
How to Improve Measurement Consistency
Use the same landmarks
Small changes in waist, neck, or hip tape position can change the estimate. Mark the anatomical location mentally and repeat it.
Keep the tape horizontal
Use a flexible, non-stretch tape. Keep it level around the body, snug against the skin, and avoid compressing soft tissue.
Repeat measurements
Take two or three readings. If they differ noticeably, reposition the tape and measure again rather than choosing the smallest result.
Track like with like
For progress tracking, use the same equation, tape, landmarks, and similar conditions each time. Do not compare values from unrelated methods as if they were interchangeable.
Circumference Estimate vs Other Methods
| Method | What it uses | Main limitation |
|---|---|---|
| Circumference equation | Tape measurements and height | Prediction depends heavily on body shape and tape technique |
| Bioelectrical impedance (BIA) | Electrical impedance and device equations | Results vary with device, hydration, and assumptions |
| Skinfold estimate | Caliper measurements at selected sites | Requires practiced measurement technique and suitable equations |
| DXA | Low-dose X-ray measurements | More costly, less accessible, and still method-dependent |
Body Composition Information Sources
Measurement and interpretation notes are based on current official military guidance and evidence reviews describing circumference-based body-composition estimates as indirect methods with prediction error.
Continue Your Health & Fitness Workflow
Compare this circumference estimate with your height-to-weight screening category using the Adult BMI Calculator, estimate resting energy and maintenance calories with the TDEE & BMR Calculator, or explore a gradual calorie and goal timeline through the Calorie Deficit & Weight-Loss Planner. For running sessions, calculate pace, splits, and projected finish times with the Running Pace & Race-Time Calculator. Use these estimates for education and planning rather than individual medical decisions.
Body Fat Calculator FAQs
Medical disclaimer: This calculator is for informational and educational use only. It provides an indirect circumference-based estimate and cannot diagnose body composition, nutritional status, or health risk. Consult a qualified healthcare professional for individual assessment, especially if a result is unexpected or you are considering changes to diet, training, or treatment.