Body fat percentage calculator
Historical body-fat estimate from height and circumferences, using branch-specific measurement sites.
Fill in the fields and the result will appear here automatically.
This historical Navy-style model estimates body fat from height and circumferences. Centimetres are converted to inches before applying the logarithms. The male branch uses abdomen at the navel and neck; the female branch uses natural waist, hips and neck. It is neither a current military eligibility assessment nor a direct body-composition measurement.
How it works
Formula and logic
Convert cm to inches by dividing by 2.54. Male estimate = 86.010log10(A−N) − 70.041log10(H) + 36.76; female = 163.205log10(W+P−N) − 97.684log10(H) − 78.387. H is height, N neck, A abdomen, W waist and P hips, all in inches. The circumference difference must be positive; only percentages strictly between 0 and 100 are displayed.
Example
Male branch: height 180 cm, neck 38 cm and abdomen 90 cm → 19.927… → 19.9%. Female branch: height 165 cm, neck 32 cm, waist 72 cm and hips 96 cm → 26.679… → 26.7%.
Fields and units
- Sex — Male / Female
- Height — cm
- Neck circumference — cm
- Abdomen / waist for selected equation — cm
- Hip circumference — cm
How to use
- — Select the male or female branch and enter height and neck circumference in cm.
- — For the male branch, measure the abdomen at the navel; for the female branch, use the narrowest natural waist.
- — The female branch also needs hips around the greatest protrusion of the buttocks.
- — Avoid pulling the tape tight or drawing in the abdomen; keep the measurement protocol consistent between dates.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- US Navy, February 2025: historical circumference measurement sites, not current eligibility rules US Army, 26 March 2019, p. 3, §f: historical use of the exact inch-based coefficients
- Limitation
- The adopted coefficients appear in the US Army's 2019 document (p. 3, §f); their derivation in the complete original NHRC reports remains unverified. This historical circumference model is neither a current Navy assessment nor a measurement or medical conclusion; no universal individual accuracy is promised.
FAQ
How accurate is the circumference body-fat estimate?
A universal error margin is not established for every visitor. Tape measurements, build and model applicability affect the result; a decimal place is display precision, not measurement accuracy.
Where should abdomen, waist and hips be measured?
Male abdomen is measured at the navel; female waist at the natural waist and hips at the greatest buttock protrusion. Neck is measured below the larynx.
Why do the two body-fat branches differ?
They are separate regression models with different circumference inputs. The selector changes the equation, not merely a label.
Why does a body-fat percentage model require height?
Height enters the logarithmic regression term. Circumferences alone do not reproduce this model.
When is this circumference calculation rejected?
For nonpositive measurements, an unknown branch, nonpositive A−N or W+P−N, or a percentage outside 0–100%. The female equation does not separately require W>N.
Why is no healthy body-fat category displayed?
Age, individual goals and medical context are not assessed. A universal health cut-off cannot be inferred from this result.
Is this a medical standard or a current Navy assessment?
No. It is a historical estimate; current military procedures can change. This number alone cannot determine health or prescribe a diet.