Body Fat (YMCA) Calculator
The YMCA body fat method estimates body fat percentage from just two numbers: waist circumference and body weight. It is one of the simplest field estimates available, needing only a tape and a scale, which is why it became popular in fitness centers. This calculator applies the standard YMCA equation to your figures and returns an estimated body fat percentage. For men the formula is minus 98.42, plus 4.15 times the waist in inches, minus 0.082 times weight in pounds, all divided by weight and multiplied by 100. The women's version uses different constants to reflect typical body composition differences. Enter a 36 inch waist and a body weight of 180 pounds for a man and the tool returns about 20.12 percent body fat. Because the method relies on only two measurements, it is a quick screen rather than a precise reading, and it works best for tracking change over weeks rather than judging a single day. Take the waist measurement at the navel, standing relaxed, and weigh yourself consistently. The complete formula and a worked example that reconciles exactly to the calculator above appear in full below, so you can follow each arithmetic step and reproduce the result by hand.
The YMCA method estimates body fat from waist and weight: for men, %BF = (-98.42 + 4.15 x waist - 0.082 x weight) / weight x 100. A 36 inch waist at 180 lb gives about 20.12% body fat.
YMCA body fat formula
Men: %BF = (-98.42 + 4.15 x waist - 0.082 x weight) / weight x 100
Women: %BF = (-76.76 + 4.15 x waist - 0.082 x weight) / weight x 100
waist in inches, weight in pounds
The waist and weight terms are combined with published constants, divided by weight and multiplied by 100 to give a body fat percentage. The men's and women's equations differ only in the constant term.
Worked example
A man with a 36 inch waist and a body weight of 180 pounds.
- 4.15 x 36 = 149.40
- 0.082 x 180 = 14.76
- Numerator = -98.42 + 149.40 - 14.76 = 36.22
- %BF = (36.22 / 180) x 100 = 20.12%
These are the calculator's default inputs, so the result above matches the widget exactly.
Body Fat (YMCA) Calculator: frequently asked questions
How does the YMCA body fat method work?
It estimates body fat from just waist circumference and body weight, using published constants. It is a quick field screen rather than a precise lab measurement, and it is useful mainly for tracking change over time.
Is the YMCA method accurate?
It is less accurate than methods such as skinfold calipers or DEXA scanning because it ignores most of the body, but it is fast and repeatable. Treat the result as an estimate and look at the trend rather than any single reading.
Why are the men's and women's formulas different?
Men and women carry fat differently, so the women's equation uses a different constant term to reflect that. The waist and weight coefficients are the same. Selecting the correct sex applies the matching constant.
Where should I measure my waist?
Measure at the level of the navel, standing relaxed, with the tape snug but not compressing the skin. Consistent placement each time matters more than a single perfect reading, especially when you are tracking change.
What body fat range is healthy?
Healthy ranges differ by age and sex. The US Centers for Disease Control and Prevention emphasizes overall activity and nutrition rather than a single body fat figure. Use any estimate as one input among several and consult a clinician for targets.
Official sources
- Physical activity and health guidance: US Centers for Disease Control and Prevention (CDC). As at 25 June 2026.
Reviewed by the CalculatorHub team, edited by James Graham, 25 June 2026. See our methodology. This is general information, not financial, tax, legal or investment advice.