You might have noticed that our linen hand sewing threads have a Nel number code to describe their thickness, like 60/2 for our ‘light’ thread. The first number refers to the weight of each strand, with higher numbers being lighter weights, and the second number being the amount of ‘plies’, or strands, that are twisted together.
A handy way to think about thread sizes is by dividing the weight number by the ply number to get the total weight. A 60/2 linen thread is 2 plies of #60 linen, so 60/2 is the same weight as #30, also known as 30/1.
Standard sewing machine thread converts to be equivalent to 120/2 in the Nel system, so 60/2 is twice the weight of standard sewing machine thread.
90/2 extra-light thread = 1.5x sewing machine threads
60/2 light thread = 2x sewing machine threads
35/2 medium thread = 3.4x sewing machine threads
25/3 heavy thread = 7.2x sewing machine threads
This same handy rule shows us that:
25/3 = 8.3
and
16/2 = 8
So 25/3 and 16/2 are very similar weights, but 25/3 is 3 ply, and 16/2 is 2 ply.
At the extreme end, hand-stitched shoes often use 8/5 to stitch on the sole, so that thread is #1.6, or the weight of 37.5 sewing machine threads bundled together!
Is that any clearer? Do you have a different way of making sense of Nel numbers?