Body Fat Calculator
Estimate body fat percentage with the U.S. Navy circumference formula, then interpret your result with a color-scored range and trend-focused guidance.
Measure at the same point each time for cleaner trend data.
Common adult range. Consistent habits can still shift this quickly.
Want a more accurate read? Estimate Body Fat %
What This Navy Body Fat Calculator Does
This calculator estimates body fat percentage from circumference measurements, not from imaging or direct tissue measurement. It uses the widely known U.S. Navy equations, which rely on logarithmic relationships between height and circumference values.
The strongest use case is consistent tracking. If you measure in the same way every time, the number can be useful for monitoring change, even when the absolute value is not perfectly exact.
Navy Formula Used
All circumference inputs are converted to inches internally, then the standard equations are applied:
Men
%BF = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
Women
%BF = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387
Weight is optional for the core equation, but this page also uses your weight to estimate fat mass and lean mass from the resulting body fat percentage. For height/weight-only lean-mass formulas, compare with the Lean Body Mass Calculator. For a circumference-and-skinfold skeletal muscle estimate, compare with the Muscle Mass Calculator.
How To Measure Correctly
Bad measurement technique is the biggest source of error. To make the output useful, keep your method fixed:
- Measure on bare skin or thin clothing.
- Keep tape level and snug, but not compressing tissue.
- Measure after normal exhale, no flexing or sucking in.
- Use the same anatomical landmark every session.
- Take 2-3 readings and average them.
- Track at the same time of day and hydration state.
Accuracy And Limitations
The Navy method is practical, cheap, and repeatable, but it is still an estimation model. Accuracy varies by body type, fat distribution, training status, and measurement precision.
People with high muscularity, atypical fat patterning, or inconsistent tape placement can see larger deviation from reference methods such as DEXA. For this reason, interpret the number as directional.
If your goal is progress tracking, the trend line over weeks is more informative than one isolated reading.
Navy Method vs Other Options
Each body-fat method answers a slightly different question:
- Navy calculator: fast, repeatable, measurement-dependent.
- Skinfold calipers: site-based fat-thickness estimate using trained pinching technique.
- Smart scales (BIA): convenient, hydration-sensitive.
- BRI: waist-height roundness estimate (try the BRI Calculator).
- BAI: hip-height adiposity estimate (try the BAI Calculator).
- DEXA: stronger lab reference, higher cost and lower frequency.
- Photo estimation: useful visual feedback on appearance changes.
A practical setup is to use one primary method weekly (like Navy tape) and pair it with periodic visual checks to keep estimates grounded in how your physique is actually changing.
FAQ
How often should I run this calculator?
Weekly or every 2 weeks is usually best. Daily measurements create noise from hydration and gut-content changes.
Why does my result look high or low?
Small errors in waist and neck measurements can shift the result a lot. Re-check tape placement first before changing your plan.
Is this medical advice?
No. This is a fitness estimation tool and educational resource. For clinical decisions, use qualified medical guidance.
References
- Hodgdon JA, Beckett MB. Body fat assessment equations developed for military circumference methods (U.S. Navy).
- U.S. Navy Physical Readiness Program Guide 4 (Body Composition Assessment):Official Navy guidance
- U.S. Centers for Disease Control and Prevention (CDC), adult weight and body-composition context:CDC BMI overview
- Internal guides:Why methods disagree | Calculator vs estimator