What this calculator does
This calculator estimates your body fat percentage using skinfold caliper measurements and the Jackson-Pollock formulas, which are among the most validated and widely used methods in exercise science.
You choose between the 3-site and 7-site protocols. The 3-site method is faster and uses fewer measurements, while the 7-site method covers more of the body and can produce more precise results. Both methods require a skinfold caliper, which measures the thickness of a pinched fold of skin and the fat beneath it at specific locations on the body.
Along with body fat percentage, the calculator shows your fat mass, lean mass, and a classification that tells you where your results fall on the standard fitness spectrum for your sex.
Jackson-Pollock formulas
The Jackson-Pollock method uses a two-step process. First, skinfold measurements are used to estimate body density. Then the Siri equation converts body density to body fat percentage.
**3-Site Protocol (Men):** Sites are chest, abdomen, and thigh. Body Density = 1.10938 - (0.0008267 x sum) + (0.0000016 x sum squared) - (0.0002574 x age)
**3-Site Protocol (Women):** Sites are tricep, suprailiac, and thigh. Body Density = 1.0994921 - (0.0009929 x sum) + (0.0000023 x sum squared) - (0.0001392 x age)
**7-Site Protocol (Men):** Sites are chest, abdomen, thigh, tricep, subscapular, suprailiac, and midaxillary. Body Density = 1.112 - (0.00043499 x sum) + (0.00000055 x sum squared) - (0.00028826 x age)
**7-Site Protocol (Women):** Same seven sites. Body Density = 1.097 - (0.00046971 x sum) + (0.00000056 x sum squared) - (0.00012828 x age)
**Siri Equation (body density to body fat %):** Body Fat % = ((4.95 / Body Density) - 4.50) x 100
How to take skinfold measurements
Accurate measurements depend on consistent technique. Use a quality skinfold caliper and follow these steps:
1. Pinch the skin firmly between your thumb and index finger, lifting the fold away from the underlying muscle. 2. Place the caliper jaws about 1 cm away from your fingers, perpendicular to the fold. 3. Release the caliper handles while still holding the fold, and read the measurement after 2 to 3 seconds. 4. Take each measurement twice and average the values. If readings differ by more than 2 mm, take a third measurement.
**Site locations:** - **Chest:** Diagonal fold midway between the armpit and nipple. - **Abdomen:** Horizontal fold about 1 inch to the right of the navel. - **Thigh:** Vertical fold on the front of the thigh, midway between the hip crease and the top of the kneecap. - **Tricep:** Vertical fold on the back of the upper arm, halfway between the shoulder and elbow. - **Subscapular:** Diagonal fold just below the lower angle of the shoulder blade. - **Suprailiac:** Diagonal fold just above and in front of the hip bone. - **Midaxillary:** Vertical fold on the mid-axillary line (side of the torso) at the level of the bottom of the sternum.
For consistent results, always measure on the same side of the body (typically the right side) and take measurements at the same time of day, ideally before exercise.
Understanding your results
Body fat percentage is divided into categories that reflect different levels of health and fitness. The ranges differ between men and women due to physiological differences in essential fat storage.
**Men:** - Essential Fat: 2 to 5 percent (minimum needed for organ function) - Athletes: 6 to 13 percent - Fitness: 14 to 17 percent - Average: 18 to 24 percent - Obese: 25 percent or higher
**Women:** - Essential Fat: 10 to 13 percent (includes reproductive fat) - Athletes: 14 to 20 percent - Fitness: 21 to 24 percent - Average: 25 to 31 percent - Obese: 32 percent or higher
Your **lean mass** is everything in your body that is not fat: muscle, bone, water, and organs. Tracking lean mass over time can help you determine whether you are gaining muscle or losing it, which body weight alone cannot tell you.
How to use
1. Select your sex using the Male or Female toggle. 2. Choose your measurement method: 3-Site or 7-Site. 3. Enter your age and body weight. You can switch between pounds and kilograms. 4. Enter each skinfold measurement in millimeters using a caliper. Hover over the field labels for tips on finding each site. 5. Click Calculate Body Fat to see your results. 6. Review your body fat percentage, classification, fat mass, and lean mass.
FAQs
Q: How accurate is the skinfold method? A: When performed correctly by a trained tester, the Jackson-Pollock method has a standard error of about 3 to 4 percentage points. The 7-site protocol is generally more accurate than the 3-site version because it samples more areas of the body. Accuracy drops significantly if technique is inconsistent or the formula is applied to populations very different from those used to develop it.
Q: Can I measure myself? A: You can, but self-measurement is harder to do consistently. It is difficult to pinch and measure at the same time, especially for sites on your back. For the most reliable results, have a trained partner take your measurements. Consistency in technique matters more than any single precise measurement.
Q: What equipment do I need? A: You need a skinfold caliper. Plastic calipers are inexpensive and work well for regular tracking. Metal spring-loaded calipers (such as Lange or Harpenden) are more precise and used in research settings, but for practical purposes a calibrated plastic caliper is sufficient.
Q: How often should I measure? A: Changes in body composition happen slowly. Measuring every 4 to 8 weeks gives enough time for meaningful changes to accumulate and avoids the noise of daily fluctuations in hydration and other factors.
Q: Why does the formula use age as a variable? A: Body density decreases with age even at the same skinfold thickness. As people age, fat tends to distribute more internally (around organs) rather than subcutaneously (under the skin), so the same external measurement reflects more total fat in older individuals.
Q: Is this the same as a DEXA scan or hydrostatic weighing? A: No. DEXA and hydrostatic weighing are considered more accurate gold-standard methods. The skinfold method is a practical field test that estimates body fat without specialized equipment. It is widely used in fitness assessments but should not be used for medical diagnosis.
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