This body fat percentage 7 site skinfold calculator measures the fat layer in seven places of the body to provide body density, fat and lean body mass. Below the form you can find information on how to perform the test and which formulas to use according to subject gender.
How does the body fat percentage 7 site skinfold calculator work?
This health tool uses the Jackson and Pollock skinfold formulas to transform skinfold measurements, taken with calipers from seven places of the body, into body fat percentage, respectively body fat mass and lean mass.
The body fat percentage 7 site skinfold calculator requires the following input:
■ Gender – because the formulas to be applied are gender specific.
■ Age – the formulas are also adapted according to subject age.
■ Chest – diagonal fold, one half the distance for men and one third of distance for females, between anterior axillary line and nipple.
■ Abdomen – vertical fold, 2 cm to the right side of umbilicus.
■ Thigh – vertical fold on the anterior midline of the thigh, half way between the proximal border of the patella and the hip.
■ Triceps – vertical fold on the posterior midline of the upper arm, halfway between the bony processes (shoulder and elbow). The arm should be held freely to the side of the body.
■ Axilla – vertical fold on the midaxillary line at the level of the xiphoid process of the sternum.
■ Subscapula – diagonal 45 degrees fold, 1-2 cm below the angle of the scapula.
■ Suprailiac – diagonal fold, immediately superior and in line with the angle of the iliac crest, on the anterior axillary line.
The seven measurements above must be input in millimeters and should be taken from the same side of the subject, usually the right side.
This method is considered the more accurate than the US navy tape measure which uses the neck, waist and hip circumferences. The only criticism received relates to the caliper test not being precise enough and to the fact that this can only account for under skin fat deposits.
Jackson and Pollock 7 site formula
In order to obtain the body fat percentage value, the skinfold results are input in gender specific formulas that generate the body density of the subject:
Body density for females:
D = (1.097 - (0.00046971 x (Chest + Abdomen + Thigh + Triceps + Axilla + Subscapula + Suprailiac)) + (0.00000056 x (Chest + Abdomen + Thigh + Triceps + Axilla + Subscapula + Suprailiac)2) - (0.00012828 x Age))
Body density for males:
D = (1.112 - (0.00043499 x (Chest + Abdomen + Thigh + Triceps + Axilla + Subscapula + Suprailiac)) + (0.00000055 x (Chest + Abdomen + Thigh + Triceps + Axilla + Subscapula + Suprailiac)2) - (0.00028826 x Age))
The SIRI formula is then used to transform body density in fat percentage:
BF% = 495/ D - 450
Body fat mass is obtained by multiplying the body fat percentage with the weight and then diving to 100.
The lean body mass can then be estimated as difference between the weight and body fat mass.
There are two more calculations performed based on Jackson and Pollock formulas, one for fat percentage from 3 sites and another from 4 sites. Similar to this, there is another skinfold formula for 4 sites, devised by Durnin and Womersley.
Example of a calculation
Taking the case of a female aged 34, weighing 128 lbs and having the following skinfold measurements:
Chest = 15; Abdomen = 26; Thigh = 17; Triceps= 11; Axilla = 15; Subscapula= 16; Suprailiac = 9;
The calculation result is:
■ Body fat percentage = 22.29%;
■ Body fat mass = 28.5 lbs;
■ Lean body mass = 99.5 lbs;
■ Body density = 1.05 x 103 kg/m3
Because fat percentages can offer information on the fitness levels of the body, the American Council on Exercise devised the following:
|Status||Females (% BF)||Males (% BF)|
|Essential fat||10 - 13||2 - 5|
|Athletic build||14 - 20||6 - 13|
|Fitness||21 - 24||14 - 17|
|Above but acceptable||25 - 31||18 - 25|
1) Jackson AS, Pollock ML, Ward A. (1980) Generalized equations for predicting body density of women. Med Sci Sports Exerc; 12(3):175-81.
2) Jackson AS, Pollock ML. (1978) Generalized equations for predicting body density of men. Br J Nutr; 40(3):497-504.
3) Aristizábal JC, Restrepo MT, Amalia L. (2008) Validation by hydrodensitometry of skinfold thickness equations used for female body composition assessment. Biomedica; 28(3):404-13.
4) Jackson AS, Ellis KJ, McFarlin BK, Sailors MH, Bray MS. (2009) Cross-validation of generalised body composition equations with diverse young men and women: the Training Intervention and Genetics of Exercise Response (TIGER) Study. Br J Nutr; 101(6): 871–878.08 Nov, 2016