Why two yarns with the same Nm can look different
You often hear this phrase:
“But how is this possible? They have the same Nm, yet they look like different yarns!”
It's a perfectly legitimate question.
The Nm indicates the theoretical thickness, but it doesn't tell the whole story of the yarn.
Let's see why.
Nm measures weight, not appearance
The Nm count only tells you: 👉 how many meters of yarn are in one gram
It says nothing about:
-
softness
-
volume
-
compactness
-
hand
-
visual appearance
Two yarns can therefore have the same weight and the same length, but behave in completely different ways.
1️⃣ Fiber type
The fiber used changes everything.
For the same Nm:
-
a cashmere appears more full and soft
-
a worsted wool is more compact
-
a cotton appears more rigid
-
a recycled yarn may seem more voluminous
👉 Different fibers = different perception.
2️⃣ Carded or worsted yarn
-
Carded:
-
more air inside
-
fuller appearance
-
softer hand
-
-
Worsted:
-
aligned fibers
-
smoother surface
-
more compact yarn
-
👉 Two identical Nm, but completely different volume.
3️⃣ Yarn twist
The twist has a huge impact.
-
low twist → softer and "chubby" yarn
-
high twist → drier and more compact yarn
A highly twisted yarn can seem thinner, even with the same Nm.
4️⃣ Number of plies (plied yarn)
An Nm 2/28 and an Nm 1/14 have a similar count, but:
-
the ply is more regular
-
it holds up better to processing
-
it has a different visual result
The way the threads are joined changes the final structure.
5️⃣ Finishing and treatment
Washing, fulling, and finishing modify:
-
volume
-
hand
-
elasticity
An already treated yarn will appear fuller than a raw one, even if the Nm is identical.
Imagine two down jackets:
-
same weight
-
same declared volume
One is goose down, the other is synthetic.
👉 On paper, they are the same.
👉 In reality, they are not.
The exact same thing happens with yarns.
The Nm is fundamental, but it's not enough on its own to understand a yarn.
To truly evaluate a thickness, you must consider:
-
fiber
-
processing
-
twist
-
structure
-
finish
That's why touching the yarn, trying it, and knowing its origin remains irreplaceable.