Body fat for females aged 20 to 29
The Navy method turns tape measurements into a body fat percentage. Use the form for your own numbers, or read the example for a woman in her 20s with a 28 inch waist, a 37 inch hip and a 12.5 inch neck.
How it works
The page measures everything in inches. It takes log10 of waist plus hip minus neck, multiplies by 163.205, subtracts 97.684 times log10 of height and subtracts 78.387. That is the female Navy estimate. For a woman in her 20s the height on this page is 64 inches and the waist is 28 inches.
Worked example
Take a woman in her 20s who is 5 ft 4 in tall with a 28 inch waist, a 37 inch hip and a 12.5 inch neck. Waist plus hip minus neck is 52.5 inches. The base 10 log of 52.5 is 1.72016. Multiply by 163.205: 1.72016 × 163.205 = 280.739. The base 10 log of 64 is 1.80618. Multiply by 97.684: 1.80618 × 97.684 = 176.435. Then 280.739 − 176.435 − 78.387 = 25.92. That is 25.9 percent body fat, in the average range.
Common questions
How accurate is the Navy method?
It is an estimate. It is usually within a few percentage points of more precise methods, and careful measuring matters. For a woman in her 20s at 5 ft 4 in, a reading of 25.9 percent could be a few points higher or lower in practice.
Where do I place the tape?
Measure the neck just below the larynx. For men measure the waist at the navel. For women measure the waist at its narrowest point and the hips at their widest. Keep the tape snug and level without squeezing. For a woman in her 20s at 5 ft 4 in the waist number is 28 inches and the neck number is 12.5 inches.
Does age change the result?
The formula does not use age. The same measurements give the same estimate at any age. A woman in her 20s at 5 ft 4 in with a 28 inch waist, a 37 inch hip and a 12.5 inch neck gets 25.9 percent.
What is a healthy body fat percentage?
Ranges depend on sex and goals. The American Council on Exercise lists essential fat, athletes, fitness, average and obesity ranges. At 25.9 percent, a woman in her 20s at 5 ft 4 in falls in the average range, which spans 25 to 31 percent.
Why does the waist matter more than weight?
Waist size reflects fat carried around the middle, while body weight cannot tell fat from muscle. For a woman in her 20s, a waist of 28 inches against a height of 64 inches gives a waist-to-height ratio of 0.44.