How to Calculate Yarn Diameter from Count

Finding Yarn diameter of a given count of yarn:
Yarn Diameter from Count can be found out by extracting the square root of the total yards in a pound of the given count and then subtracting 10 percent from the result. The yarn diameter in inches is reciprocal. In this article, we know how to calculate yarn diameter from the count.

The yarn diameter affects many technical settings of various processes.  Slub catcher setting is chosen according to yarn diameter. The yarn diameter greatly influences the decision-making process of correct reed count selection in warping and weaving.

How to Calculate Yarn Diameter from Count

For example:

  • Find out the diameter of a 46s yarn.

Yards in a pound (840 x 46)
Square root 166.6
Less 10% 177.0
Hence the diameter of 1/177 inch

How to Calculate Yarn Diameter from Count
Fig: Estimating Yarn Diameter with Machine

In other words, if 177 threads are laid side by side they occupy one inch
The diameter of yarns vary as the square root of the yarn counts
Thus the diameter of 36s is 1/157 inch
And 16s is 1/104 inch

This can be shortened in a simple equation as bellows

Diameter per inch (cotton/spun silk) = √(yards per pound) – 10%
= 0.9 √yards per pound
= 26.1 √count

Calculate yarn diameter from count is very useful particularly in weaving for determining the optimum ends and picks per inch. Intersections of warp end for weft threads and weft threads for warp have to be carefully considered. This is also useful for finding ends and picks while changing from one count to another, for finding the counts in changing from one number of threads per inch to another number of threads per inch, and for finding ends and picks per inch in use and in changing from one pattern to another.

Mathematical problem:

Find out the diameter of 20s count of yarn.


Diameter per inch = √ ( yards per pound) – 10%
Here yards per pound = (20 x 840)

So, now

Diameter per inch = √(yards per pound) – 10%
= √ (20 x 840 ) – 10%
= 118 per inch (ANS)

Author of this Article:
Amit Kumar Das
Founder of "টেক্সটাইল ম্যানিয়া" Blog
Pabna Textile engineering college, Pabna, Bangladesh
Cell: 01770 456240
Email: [email protected]

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