Body Composition
US Navy formula for men
The logarithm is base 10 and all circumferences are in centimetres. The subtraction of 450 converts the ratio into a percentage.
The Formula
BF% = 495 / (1.0324 - 0.19077 x log(waist - neck) + 0.15456 x log(height)) - 450
The logarithm is base 10 and all circumferences are in centimetres. The subtraction of 450 converts the ratio into a percentage.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| waist - neck | Abdominal girth net of neck size | centimetres | For a 90 cm waist and 38 cm neck this is 52, whose base-10 logarithm is 1.7160033436347992. |
| height | Standing height | centimetres | For 180 cm the base-10 logarithm is 2.255272505103306. |
| BF% | Estimated body fat percentage | percent | For the worked case this is 19.811988411785478%. |
What Each Symbol Means
waist - neckcentimetres
Abdominal girth net of neck size
For a 90 cm waist and 38 cm neck this is 52, whose base-10 logarithm is 1.7160033436347992.
heightcentimetres
Standing height
For 180 cm the base-10 logarithm is 2.255272505103306.
BF%percent
Estimated body fat percentage
For the worked case this is 19.811988411785478%.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate body fat percentage page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Body Fat Percentage, filed under Health. Every number the guide produces comes from substituting into this one line.