Learn How To Somatotype


Most likely you have come to this website because you want to know your somatotype. There are many reasons why you might like to have this information:  athletic development, weight control, health, personal training, temperament identification or just ordinary curiosity. The purpose of this free tutorial is to show you how to discover your somatotype.  After you find your somatotype you may be inclined to do the same for others especially if you are able to add the value of this information to a service you are providing.

This website focuses on the Trunk Index  method of somatotyping that is based on William H. Sheldon’s lifelong search to create an objective technique for determining a person’s somatotype. It has been 35 years since Sheldon’s death and for all practical purposes his death was the end of the development of his methods. New technologies have become widely available and I have updated some techniques for this tutorial. Digital photography allows instant editing and review to make sure you get a usable photograph. There is no need to wait for a dark room that slows down the process.  Digital photography makes it possible to take a  picture of yourself and eliminate the possibility of your private photo ending up exposed to eyes that aren’t interested in the science of somatotyping.  Also, there are computer programs that replace the need to use an obscure drafting instrument called a “planimeter”.  A planimeter is used to measure the area of irregular polygons. Measuring the area of irregular polygons is essential to determine the very important Trunk Index.  The importance of the Trunk Index will be explained later.  For now it is enough to know that it involves measurements made of certain areas on a subjects photograph.

Sheldon’s original research was centered around discovering some way of measuring the human body  that would enable researchers and various practitioners to sort and classify the human physique.  There are hundreds of measurements that could be made and correlated.  But which ones are easily identifiable as first order criteria.  In other words, what are the basic dimensions that capture the differences between one person’s physique and another person’s physique.  There was an ancient intuition that people could be described roughly as: fat or thin, strong or weak, tall or short. Actually we do this all the time. Humans have a rough scale they  apply to these dimensions.  Not being satisfied with describing people as just tall or short we also use various adjectives to express degree: very tall, average, average but a little on the tall side, very short. We even mix dimensions: tall and heavy, short and skinny, average height and stocky. Sheldon wanted to see if these intuitions about physique could be measured and expressed on some sort of consistent scale thus generating a practical scientific taxonomy (a system of classifying biological organisms).

Before he could systematically begin measuring human differences he needed to get an idea of what he should measure.  To do this he photographed thousands of nude subjects posed in defined positions: feet positioned shoulder width apart, arms slightly extended away from the body, front, side and back..  Nobody ever did this before Sheldon, even though photography had been  available for close to a century. We’re not talking about “genius”. With a little practice ordinary observant humans are very good at sorting things according to similarities and differences.  Anyone with a few thousand samples of anything could sort them out according to how they look.  Sheldon, confirmed  that there were basically three dimensions to the human physique. His terms for them were endomorphy (emphasis on the belly) , mesomorphy (emphasis on the upper torso) and ectomorphy (emphasis on extension – height).  Sheldon was criticized for his terms because he took the liberty and presumed a relationship between the somatotype dimensions and the three layers of a developing embryo. Scientists don’t like end runs that avoid substantial research. But, in spite of this criticism, his terms have persisted indicating that there  hasn’t been a total rejection of this insight.

What does all this have to do with why you should learn the Trunk Index method of somatotyping?   Sheldon discovered that the Trunk Index is the key to objectively represent the third dimension for classifying the human body.  Some critics have argued that there are only two dimensions; height and weight (mass). Sheldon clearly saw three dimensions in his photo collection – height and two types of mass (weight). The body is organized to carry out the functions of : 1) energy production and storage 2) energy expenditure. Endomorphy takes care of energy and energy storage,  while Mesomorphy is invested in forming muscle.  Endomorphy is NOT fat. Mesomorphy is NOT muscle. Endomorphy is in the fat business.  Mesomorphy is in the muscle business.   After working with the Trunk Index Sheldon concluded that he had been subjectively considering the ratio of the thoracic trunk (upper torso) to the abdominal trunk (gut area) when he was classifying somatotypes.

The fact that there is something we can label the Trunk Index somatotype method  suggests that there is another method.  Actually, the dominant method is the Heath-Carter System.  If you want to find out more about their method there is an easy to find PDF available by searching for “Heath Carter”.   Barbara Honeyman Heath Roll, served as an assistant to Sheldon for a while.  Their conflicts would make an interesting drama about love and hate in academia.  The Heath-Carter method differs from Sheldon’s in some very significant philosophical ways.

Barbara…Roll abandoned the “character (temperament) reading” features that originally motivated Sheldon.  She joined up with Lindsay Carter applying her technique to the concerns of the sports world.   Coaches and trainers are interested in finding the best specimens for their particular sport.  After they find the best available candidates their concern is with maintaining the athletes in prime condition and if possible improve their condition.  This involves a philosophy heavily emphasizing the body’s plasticity. Consequently the Heath-Carter method uses calipers to measure sub-cutaneous fat and bone width.  A tape measure is used to measure the circumference of biceps for tracking muscle growth.  One other major difference is the fact that they make no exception for the differences between male and female. A female with a somatotype of 3,4,5 would have the same height and other measurements  as a male 3,4,5.

While Heath-Carter might work in the sports world it falls short as a tool in predicting
temperament.  Measuring skin fold thickness is measuring sub-cutaneous fat,  NOT endomorphy.  Endomorphy is NOT fat but the propensity to become fat. Measuring the circumference of  biceps is measuring muscle NOT mesomorphy.  Mesomorphy is NOT muscle but the propensity to easily increase muscle mass.  Therein lies the difference between Sheldon’s method and the Heath-Carter method which dominates in the sports field.  If you want to track the development of athletes the Heath-Carter method is preferred because it perceives a person’s physique as changeable.  However, if you are looking for constitutional/psychological correlations in addition to variables in fat accumulation and muscle development then the Trunk Index method gives you the best of both worlds.

To be sure there is a lot of controversy and debate over some of these topics.  This
section is not for addressing various arguments concerning somatotype.  Why argue about something you might not know much about?  Learn Sheldon’s method.  Discover YOUR somatotype.  Work with it. Get your feet wet. Test the water. Then dive in for a good swim.

Let me assure you this is quite easy to learn.  If you have questions because something isn’t clear please email me at jdanzer@mysomatotype.com .  Remember your questions and suggestions are essential.. This website isn’t meant to be static.  I want it to be both informative and responsive to make it easy to use.

The Question of Accuracy

A word of caution before we get into the nuts and bolts of somatotyping.  You need to rid yourself of the notion that you have to be extra careful to get the correct assessment.  The main thing is that you get the rank order of the various dimensions right.  It isn’t so important whether a person is  a 6,4,2 or a 6,4,1½ but rather that the person is predominantly an endomorph (6) next mesomorph (4)  and finally ectomorph (1½) . This is especially the case when looking at the effects on temperament.

When a scientist investigates an area that hasn’t received a lot of scientific attention there is a tendency to become obsessed with accuracy.  You just can’t afford to leave anything out of the picture.  Reviewers of research expect to see decimal places – the more the better.  Too many round numbers suggests a careless investigation.  Sheldon certainly went through that stage. He became absorbed in fractions of inches and pounds.  This was a necessary initial stage.  But even with his final Trunk Index method his tables for identifying a somatotype were unnecessarily cumbersome with odd fractions of height and the superfluous Somatotype Ponderal Index  (Height in inches divided by the cube root of the weight).

Of course Barbara Heath (Heath-Carter Somatotype Method) was concerned about precision so she could lay claim to scientific rigor. The Heath-Carter somatotype method measures weight to 1/10 of a kilogram, height to the nearest millimeter and muscle girth to nearest 1/10 millimeter.  Is it any wonder that the Heath-Carter Method views a person’s somatotype as being variable?   A little water weight and you increase your endomorphy rating.  Common sense should tell you that those minute variations are not going to make a significant difference in either temperament or physical performance.  So put the perfectionism aside.  Relax and follow these easy (relatively easy) instructions.



a. Measuring Height  

b. Measuring Weight  


a. Taking the Somatotype Photo  

b. Marking the Areas of the Physique for the Trunk Index.

c. Measuring the Marked Areas to Determine the Trunk Index


a.  Determining the Somatotype Using the Somatotype Tables

b.  Ranking the Order of the Body Systems.

c.  Implications of the Somatotype Ranking