Body fat for females aged 40 to 49
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 40s with a 30 inch waist, a 38 inch hip and a 13 inch neck.
How it works
Start with waist plus hip minus neck in inches. Take the base 10 log and multiply by 163.205. Take the base 10 log of height and multiply by 97.684. Subtract the second result from the first and then subtract 78.387. The neck on this female page is 13 inches and the height is 64 inches.
Worked example
Measure first. A woman in her 40s at 5 ft 4 in with a 30 inch waist, a 38 inch hip and a 13 inch neck gives a base of 55 inches. Take the base 10 log to get 1.74036. Multiply: 1.74036 × 163.205 = 284.035. The base 10 log of the height, 64 inches, is 1.80618. Multiply: 1.80618 × 97.684 = 176.435. Combine them: 284.035 − 176.435 − 78.387 = 29.21. Rounded, that is 29.2 percent, in the average range.
Common questions
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 40s at 5 ft 4 in with a 30 inch waist, a 38 inch hip and a 13 inch neck gets 29.2 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 29.2 percent, a woman in her 40s 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 40s, a waist of 30 inches against a height of 64 inches gives a waist-to-height ratio of 0.47.
Can I enter centimeters?
Yes. Switch the units and the page converts everything to inches before it does the math. For a woman in her 40s at 5 ft 4 in, a waist of 30 inches is 76.2 cm and a neck of 13 inches is 33.0 cm.
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 40s at 5 ft 4 in, a reading of 29.2 percent could be a few points higher or lower in practice.