If you do not have calipers or a full set of tape measurements, the YMCA method offers the simplest body fat estimate there is: two numbers, weight and waist. It comes from the fitness assessment procedures that YMCA centres in North America have used for decades, and the equation sits in the YMCA of the USA’s Fitness Testing and Assessment Manual. It is a quick way to get a rough idea of body composition and to track change from month to month.
Because it uses only two inputs, it cannot account for muscle, frame size or fat distribution, and it should be seen as a screening tool.
How to use the YMCA body fat calculator
- Select your sex. The constant in the equation differs for men and women.
- Enter your weight in pounds or kilograms.
- Enter your waist circumference at the navel, in inches or centimetres.
- Read the estimate, its ACE category and the fat and lean mass in your body.
YMCA body fat formula
Women: %BF = (−76.76 + 4.15 × waist (in) − 0.082 × weight (lb)) ÷ weight (lb) × 100
The equations are given in the YMCA of the USA, YMCA Fitness Testing and Assessment Manual (Golding LA, ed., 4th edition, 2000). The numerator is an estimate of fat mass in pounds, and dividing it by body weight gives the percentage. Fat mass = weight × %BF ÷ 100.
Worked example
A man weighing 180 lb with a 34-inch waist.
- Numerator = −98.42 + 4.15 × 34 − 0.082 × 180 = −98.42 + 141.10 − 14.76 = 27.92 lb of fat
- Body fat = 27.92 ÷ 180 × 100 = 15.5%
- Category: Fitness (ACE).
A woman weighing 140 lb with a 30-inch waist gets (−76.76 + 124.5 − 11.48) ÷ 140 × 100 = 25.9%, in the average category.
Estimated body fat for men
| Weight (men) | Waist 30 in | Waist 34 in | Waist 38 in | Waist 42 in |
|---|---|---|---|---|
| 130 lb (59 kg) | 11.9% | 24.6% | 37.4% | 50.2% |
| 150 lb (68 kg) | 9.2% | 20.3% | 31.3% | 42.4% |
| 170 lb (77 kg) | 7.1% | 16.9% | 26.7% | 36.4% |
| 190 lb (86 kg) | 5.5% | 14.3% | 23.0% | 31.7% |
| 210 lb (95 kg) | 4.2% | 12.1% | 20.0% | 27.9% |
Estimated body fat for women
| Weight (women) | Waist 26 in | Waist 30 in | Waist 34 in | Waist 38 in |
|---|---|---|---|---|
| 110 lb (50 kg) | 20.1% | 35.2% | 50.3% | 65.4% |
| 130 lb (59 kg) | 15.8% | 28.5% | 41.3% | 54.1% |
| 150 lb (68 kg) | 12.6% | 23.6% | 34.7% | 45.8% |
| 170 lb (77 kg) | 10.1% | 19.9% | 29.6% | 39.4% |
| 190 lb (86 kg) | 8.2% | 16.9% | 25.7% | 34.4% |
Body fat categories
| Category (ACE) | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | 25% and above | 32% and above |
How to get the most from it
- Measure consistently. The waist reading drives the result; a 1-inch error moves it by 2 to 3 percentage points.
- Compare like with like. Use the same method each time. For a second opinion try the Navy Body Fat Calculator or the Skinfold Body Fat Calculator.
- Look at the trend. A falling waist at stable weight is a good sign; so is a stable waist as weight rises with training.
- Be aware of the blind spots. Muscular people with large waists, or those who carry fat mainly in the limbs, will be misjudged.
Related measures
The Body Fat Calculator offers a Navy-method and BMI estimate, the Lean Body Mass Calculator shows muscle-and-organ mass, and the Waist-to-Height Ratio Calculator converts waist size into a health-risk zone. The BMI Calculator gives the weight-for-height index.
This page is for information only and is not medical or dietary advice. Speak to a doctor or registered dietitian about your own situation.
Sources
- Golding LA, ed. YMCA Fitness Testing and Assessment Manual, 4th edition. Human Kinetics for the YMCA of the USA, 2000.
- American Council on Exercise. What Are the Guidelines for Percentage of Body Fat Loss? (body fat categories).
Frequently asked questions
What is the YMCA body fat formula?
It estimates body fat from body weight and waist circumference alone. For men it is (−98.42 + 4.15 × waist in inches − 0.082 × weight in pounds) ÷ weight × 100, and for women the constant is −76.76 instead of −98.42. It appears in the YMCA’s fitness assessment manuals.
How accurate is the YMCA method?
It is a rough screening estimate, usually within several percentage points of laboratory methods for average adults, and less reliable for very muscular, very lean or very overweight people. Tape methods that include neck and hip, such as the Navy method, tend to be more precise.
Where do I measure my waist?
At the level of the navel (for the YMCA method, the abdomen at the umbilicus), standing relaxed, after breathing out normally. Keep the tape snug and level, and measure twice.
Why does a bigger waist raise the estimate?
In the formula each inch of waist adds 4.15 pounds of estimated fat mass, while each pound of body weight subtracts 0.082 pounds. In other words a larger waist at the same weight means more of the weight is assumed to be fat.
Can I use this to track progress?
Yes, with the same method and measurement technique each time. Do not compare results from different formulas, since each has its own bias. The Body Fat Calculator explains the other options.