Yarn Wraps Per Inch Calculator

WPI measurement and yarn weight classification.

Inputs

Wraps per inch (WPI)

Number of plies

Sample weight (oz)

Sample length (yd)

Tab to move between fields

Results

Yarn weight (#)

Yards/lb (McMorran)9,800

Yards/lb (measured)800

English count (Ne)30.15

Tex19.6

Yarn diameter (mm)1.81

Weight CategoryDK

Needle Size US5-7

How to Use This Calculator

Wrap your yarn snugly around a ruler for 1 inch without stretching or overlapping, then count the wraps and enter the WPI.
Enter the number of plies in this yarn.
Weigh a known length of yarn and enter both the weight in ounces and the length in yards for a measured yards-per-pound.
Read the yarn weight number (0 = lace through 6 = super bulky) to identify the standard weight category.
Compare the McMorran yards/lb (from WPI) with the measured yards/lb for a cross-check.
Use the yarn diameter in mm and the Tex/Ne counts if you need to match yarn specs to a weaving sett.

How the result changes with Wraps per inch (WPI)

Wraps per inch (WPI)	Yarn weight (#)
6.9	6
22	1
39	0
54	0

What each input means

Wraps per inch (WPI): Count of yarn wraps that fit in one inch — wrap snugly without stretching.
Number of plies: Number of singles plied together in this yarn.
Sample weight (oz): Weight of a known sample for measured yards-per-pound.
Sample length (yd): Length of the weighed sample in yards.

What each result means

Yarn weight (#): Craft Yarn Council weight number: 0=Lace through 6=Super Bulky.
Yards/lb (McMorran): Yards per pound estimated from WPI using McMorran's balance formula.
Yards/lb (measured): Yards per pound from your weighed sample.
English count (Ne): Approximate English cotton count yarn numbering.
Tex: Approximate Tex count (grams per 1000 meters).
Yarn diameter (mm): Approximate yarn diameter in millimeters.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Wraps per inch (WPI) = 14, Number of plies = 2, Sample weight (oz) = 1, Sample length (yd) = 50 = 4 input(s) provided
Calculate Yarn weight
Yarn weight
3 = 3
Calculate Yards/lb
Yards/lb = (wpi * wpi * 100) / plies
9800 = 9800
Calculate Yards/lb
Yards/lb = (sampleLengthYd / sampleWeightOz) * 16
800 = 800

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