Wool Grades and the Sheep that Grow the Wool - Comparing wool grades

Oct 22, 2026

Wool has been categorized for centuries using fiber diameter to distinguish coarse versus fine yarns, but breed differences and within-fleece variation required more precise grading. Three systems are used for manufacturing and sales: the Blood System, the Count System, and the Micron System. Tables summarize USDA grade ranges and micron-based average fiber diameter limits, including standard deviation. The Blood System links grades to Merino/Rambouillet blood fractions, the Count System relates “hanks” per pound, and the Micron System uses measured fiber diameter for accurate 16-grade classification.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages9

Reading Time23 min

AccessFree to download

Comparing wool grades

Blood System

Count System

Micron System

WoolGradesand theSheepthatGrowthe Wool # Comparing wool grades For thousands of years,wool has been spun into coarse or fineyarns—the wool fiber diameter determining whether it wouldbe coarse or fine.However,more than the terms “coarse”or"fine"were needed to describe the difference between woolfrom the different breeds of sheep,or the wool from thedifferent parts of the same fleece.So,over the years,threegrading systems evolved to describe wool for manufacturingand sales.They are the Blood System,the Count System,andthe Micron System. | Top
Wool | Old
Blood
Grade | Standard Specifications | | | | --- | --- | --- | --- | --- | | | | USDA
Grade | Range for
Average Fiber
Diameter | Standard
Deviation
Maximum | | Fine
Fine
Fine
in | Fine
ing
Fine
Fine | Finer than 80's
80's
70's
64's | (microns)
Under 17.70
17.70-19.14
19.15-20.59
20.60-22.04 | (microns)
3.59
4.09
4.59
5.19 | | Medium
Medium
Medium
Medium
Medium
Medium | K Blood
W Blood
%Blood
%Blood
X Blood
X Blood | 62's
60's
58's
56's
54's
50's | 22.05-23.49
23.50-24.94
24.95-26.39
26.40-27.84
27.85-29.29
29.30-30.99 | 5.89
6.49
7.09
7.59
8.19
8.69 | | Coarse
Coarse
Coarse | Low4
Low%
Common | 48's
46's
44's | 31.00-32.69
32.70-34.39
34.40-36.19 | 9.09
9.59
10.09 | | Very Coarse
Very Coarse
Very Coarse | Braid
Braid
Braid | 40's
36's
Coarser than 36's | 36.20-38.09
38.10-40.20
Over 40.20 | 10.69
11.19
一 | The Blood System is the oldest system,originating at the timeof the early American colonies.It is based on the bloodlineor breeding of the sheep,and is divided into six grades.TheMerino or Rambouillet wool is called fine.A half-blood woolcomes from sheep that are half Merino or Rambouillet andhalf another breed.Wool types grown on sheep with fractional (ASTM)American Society for Testing and Materials Designation D3991 Grades of wool by sheep common in the U.S. | Delaine-Me | rino | | | | | | | | | | | | | | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | | | | | | | | | | | | | | | | | Debouillet | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Rambouille | t | | | | | | | | | | | | | | | Targhee | | | | | | | | | | | | | | | | Columbia | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Coriedale | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Finsheep | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Montadale | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Dorset | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Cheviot | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Southdown | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Shropshire | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Hampshire | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Suffolk | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Oxford | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Romney | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Border Leic | ester | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Lincoln | | | |

FAQs

Why were multiple wool grading systems developed beyond simple “coarse” and “fine” categories?

Because wool differences depend not only on whether it is coarse or fine, but also on sheep breed and variations across parts of the same fleece.

What does the Blood System base wool grades on?

It is based on sheep breeding and bloodline fractions, dividing wool into six grades such as fine (Merino/Rambouillet), half-blood, and other intermediate levels.

How does the Count System define wool grades?

It uses the yarn-count concept: the number of hanks of yarn that can be spun from one pound of wool top, where higher counts correspond to finer wool.

Why is the Micron System considered the most technical and accurate method?

It classifies wool into 16 grades according to average fiber diameter measured by a micrometer, and very small micron differences define adjacent grades.

Oct 22, 2026

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