Body Mass for Women
Estimate body fat percentage and lean body mass from your age, weight, and seven skinfold measurements taken with calipers.
7-Point Skinfold Calculator for Women
Body Mass for Women Formula
Where:
- \(S\) — sum of the seven skinfold measurements (mm)
- \(Tr, Si, Th, P, Ab, Sb, Ax\) — triceps, suprailiac, thigh, pectoral, abdominal, subscapular, and axilla folds (mm)
- \(A\) — age (years)
- \(D\) — estimated body density (g/cm³)
- \(BF\) — estimated body fat (%)
- \(W\) — body weight (kg)
- \(LBM\) — estimated lean body mass (kg)
The women’s Jackson–Pollock seven-site equation estimates body density from age and skinfolds. The calculator converts density to body fat percentage using the Siri equation, then uses weight to estimate lean body mass.
Body Mass for Women – Calculation Example
Example: A 30-year-old woman weighs 60 kg. Her triceps, suprailiac, thigh, pectoral, abdominal, subscapular, and axilla measurements are 15, 20, 25, 18, 22, 19, and 16 mm, respectively.
\[S=15+20+25+18+22+19+16=135\text{ mm}\]
\[D=1.097-0.00046971(135)+0.00000056(135)^2-0.00012828(30)=1.03994675\text{ g/cm}^3\]
\[BF=\frac{495}{1.03994675}-450\approx25.99\%\]
\[LBM=60\left(1-\frac{25.9859}{100}\right)\approx44.41\text{ kg}\]
Result: Estimated body fat is 25.99%, and estimated lean body mass is 44.41 kg.
How to use the calculator
- Enter your Age in years and Weight in kilograms.
- Use skinfold calipers to measure your Triceps fold, Suprailiac fold, and Thigh fold. Enter each reading in millimeters.
- Enter the Pectoral fold, Abdominal fold, Subscapular fold, and Axilla fold, also in millimeters. Follow a consistent seven-site measurement protocol for all sites.
- Read the estimated Body fat percentage and Lean body mass in kilograms. Check that no measurement was entered in centimeters by mistake.
What the results mean
Body fat percentage estimates the share of your total weight that is fat mass. Lean body mass is everything else, including muscle, bone, organs, blood, and water. It is not a measurement of muscle mass alone. For example, the default inputs produce an estimated 25.99% body fat and 44.41 kg of lean body mass at a weight of 60 kg.
Skinfold calipers measure the thickness of a pinched layer of skin and subcutaneous fat at selected sites. The seven readings are added together; the equation uses that sum and your age to estimate overall body density. This is an indirect estimate: it does not measure all body fat or directly determine the composition of internal tissues.
A single percentage is best interpreted alongside measurement quality, changes over time, and your broader health context. There is no universal body fat target that suits every woman or every stage of life. For another way to track body size, a waist-to-height ratio calculator uses waist circumference rather than calipers, but it answers a different question.
Measurement tips and limitations
Use a suitable caliper and a consistent site guide. Identify the same landmarks each time, take measurements on the same side of the body, and record the fold thickness in millimeters. Taking repeated readings at each site can help reveal an inconsistent pinch or misplaced caliper. If possible, have the same trained person perform each assessment.
Skinfold results can vary with the measurer, caliper, site selection, and individual fat distribution. Very large or hard-to-grasp folds may be particularly difficult to measure consistently. The density-to-fat conversion also relies on assumptions about the density of fat and fat-free tissue; these assumptions may not fit everyone equally well. Treat the output as an estimate, not a diagnosis or a precise reading of your body composition.
For progress tracking, compare measurements made under similar conditions using the same method. A small change may reflect measurement variation rather than a real change in body fat. If seven sites are impractical, the 3-point body fat calculator uses fewer skinfold readings, though results from different methods should not be treated as interchangeable. If you use the lean body mass estimate in a Katch–McArdle BMR calculator, remember that uncertainty in the skinfold estimate carries through to the calorie estimate.
Frequently Asked Questions
What is a healthy body fat percentage for a woman?
There is no single healthy percentage for every woman. Commonly cited adult reference ranges are roughly 21–32%, but age, activity, and health circumstances affect how a result should be interpreted. Skinfold estimates also have measurement error, so a value near a range boundary is not a diagnosis. Ask a healthcare professional if you need an individual health assessment.
Can I enter weight in pounds or skinfolds in centimeters?
Convert both before entering them: divide pounds by 2.20462 to get kilograms, and multiply centimeters by 10 to get millimeters. For example, 132 lb is about 59.87 kg, and a 2 cm fold is 20 mm. The resulting lean body mass is in kilograms; multiply it by 2.20462 if you want pounds.
How can I calculate fat mass from the results?
Subtract lean body mass from total body weight, or multiply weight by body fat percentage divided by 100. For example, at 60 kg and 26% body fat, estimated fat mass is \(60\times0.26=15.6\) kg. This is an estimate of total fat mass, not a measurement of how much fat is at any particular site.
Does a skinfold caliper measure one layer or both sides of the pinch?
A skinfold reading is the thickness of the entire pinched fold: two layers of skin with the tissue between them. Enter the number shown by the caliper; do not halve or double it. Keep the pinch held while reading the caliper, and follow its instructions for placement and timing. Technique can substantially affect the result.
Why did I get a negative body fat percentage or an unusually high result?
An implausible result usually means the inputs or method need checking, not that the percentage is meaningful. Recheck units, site readings, and age, particularly if a fold was entered in centimeters as though it were millimeters. The equation is an estimate and can also behave poorly outside the populations and measurement conditions for which it was developed.
Is this equation suitable during pregnancy or for children?
Do not rely on this adult women’s skinfold equation to assess body composition during pregnancy or in children. Changes in body composition and the assumptions behind the equation can make its results misleading in those circumstances. A healthcare professional can advise on an appropriate assessment method if body composition information is needed for a health decision.
How does a seven-site skinfold estimate compare with a DEXA scan?
The methods do not measure body composition in the same way. Skinfolds use external measurements and a population-based equation to estimate body fat; a DEXA scan uses low-dose X-rays to estimate several body-composition components. Their percentages may differ even when both measurements are performed correctly. For tracking change, use a consistent method rather than treating results from the two as interchangeable.