Body Fat at 5'6" With a 30-Inch Waist
A man of 5'6" with a 30-inch waist and a 15-inch neck measures 10.6% body fat on the Navy tape method. That sits in the Athletes band of the ACE scale, which spans 6–13%. Losing two inches of waist at this height takes the estimate from 10.6% down to 5.6%, a shift of 5.0 points.
The arithmetic behind 10.6%
Everything reduces to two logarithms and one division. With the waist and neck in centimetres — 76.2 cm and 38.1 cm — the girth difference is 38.1 cm and the height is 167.64 cm:
- log10(38.1) = 1.5809
- log10(167.64) = 2.2244
- 1.0324 − (0.19077 × 1.5809) + (0.15456 × 2.2244) = 1.0746
- 495 / 1.0746 = 460.63, and 460.63 − 450 = 10.6
Feed the same numbers into the site's calculator and the gauge lands on the identical value — the page and the tool share one equation and one set of unit conventions.
Every waist size at 5'6"
Holding height and neck constant isolates the waist, which is the input that actually moves. Two-inch steps are shown because a tape read is rarely more precise than that.
| Waist | Centimetres | Body fat | ACE band |
|---|---|---|---|
| 28" | 71.1 cm | 5.6% | Athletes |
| 30" | 76.2 cm | 10.6% | Athletes |
| 32" | 81.3 cm | 15.1% | Fitness |
| 34" | 86.4 cm | 19.2% | Acceptable |
| 36" | 91.4 cm | 22.9% | Acceptable |
| 38" | 96.5 cm | 26.3% | Obesity |
| 40" | 101.6 cm | 29.5% | Obesity |
| 42" | 106.7 cm | 32.5% | Obesity |
| 44" | 111.8 cm | 35.3% | Obesity |
| 46" | 116.8 cm | 37.9% | Obesity |
What the band means in practice
The athletes band is what consistent training plus controlled eating produces, and it is sustainable for people who actually train. It is not a healthy default for someone who does not. Two inches more of waist at this height would push the estimate to 15.1%.
Questions about this measurement
What body fat is a 30-inch waist at 5'6"?
The US Navy circumference equation returns 10.6% for a man of 5'6" with a 30-inch waist and a 15-inch neck, which falls in the Athletes band (6–13%).
Why does the neck measurement matter?
The formula subtracts neck from waist, so the neck is not a rounding detail — one extra inch of neck with the waist unchanged lowers the estimate by 2.4 points here. Measure the neck at its narrowest point, just below the larynx, with the tape flat.
How accurate is a tape measurement?
For an adult man with average proportions the circumference method typically lands within three to four percentage points of a DEXA scan. The error grows for very lean or very heavy subjects, and it assumes a normal neck-to-waist geometry rather than a trained or unusual build.
Does height really change the number?
It does, against intuition. At the same 30-inch waist, adding two inches of height changes the estimate by 0.9 points, because the equation treats stature as a proxy for frame size: a taller frame carries the same waist with less relative fat.