The purpose:

The Bradford system is a way to assess the quality of wool.

This system is also known as the "English Worsted Yarn Count System" or "spinning count" or "Bradford count".

The method:

To measure the fineness of sheep wool fiber before microscopes and lasers were used, English wool handlers in the city of Bradford described wool by estimating (with experienced eyes) how many 560-yard hanks of single strand yarn could be made by a good spinner from a pound of "top."

• Top is cleaned combed wool with the fibers all parallel.

The finer the average diameter of a single wool fiber, the more hanks could be spun. From a pound of "64s," for example, sixty-four such hanks could be made (more than 20 miles). From the finest wools, more than 80 hanks could be spun; from the strongest, perhaps 36 or fewer. Using ranges denoted by the stronger end (that is “44s” ran up to “46s”), wool lots were classified and prices derived.

Because they were estimating with experienced eyes, it was obviously not a perfect science.  The Bradford count may be biased no matter how experienced the rater is; also it relies heavily on number of crimps (regular undulations) per inch, which has a not-very-strong correlation with actual average fiber diameter.

Other Methods Are Possible:

Although the Bradford System is still widely used among shepherds and breed associations, more objective measuring systems are replacing its use in the international market.

In 1968, the United States Department of Agriculture issued official standards (for the U.S.A. only, not applicable worldwide) which assigned ranges of average fiber diameter (AFD) and maximum standard deviation to each of the Bradford counts. For example, wool with average fiber diameter in micrometers from 28.60 to 30.09 was to be called "54s." 

More objective measurement of several fiber characteristics has become faster and more available and is likely to replace the Bradford count system in all commercial arenas. However, the spinning count (Bradford Method) will most likely not disappear completely for a while.

Learn more about wool measuring systems.

Learn about wool grades & standards.

Learn about wool classing.

Learn about a wool bale.