For a few years now I have made up sets of fine lambswool and cashmere yarn for you to use in your own visible mending and darning projects. I often get asked what weight they are, normally with reference to hand knitting yarns.  I’ve found this a bit tricky to answer, so I’ve been trying to work out the comparison.  

Hand knitting yarn weights vary. They vary in what they’re called (there’s a difference between the UK and the US, and Australia seems to be different again!). Within each weight of hand knitting yarn there can be a lot of variation in thickness, so I find hand knitting yarn terms to be a bit vague.

How the thickness of the yarns I use are measured 

As you may know I’m a knitwear designer as well as a mender, so I work with very fine commercial knitting yarns on my knitting machines. These are perfect for mending because they’re so fine, and I use a wide range of really lovely colours.

These yarns are measured in New Metric count or Nm, and this is the number of 1000m (or 1km) of yarn per 1kg of weight. So if a yarn was 6Nm that would mean 6km of that yarn would weight 1kg.

I work with 1/14nm lambswool a lot in my work. The 1 is the ply of the yarn (the number of strands twisted together to make the yarn), and the second number (14) is the number of km in 1 kg. so this is a single ply yarn with 14,000m to the kilogram.

The higher the number, the finer the yarn.

Keeping up? This stuff always fries my brain a little bit!

The cashmere darning yarn I have is mostly 2/28nm. This is the same thickness as the 1/14nm yarn as it uses two strands of a yarn twice as fine twisted together.  

What’s the difference between ‘yarn’ and ‘wool’?  

Seeing as this is a more technical post, maybe I should explain the words ‘yarn’ and ‘wool’ and their differences. Yarn can be made up of any fibre or combinations of fibres, twisted and spun together. Wool is a term that specifically refers to the fibre from a sheep, but the word ‘wool’ often gets used to mean ‘yarn’.  

The term ‘darning wool’ is often used to mean a yarn or thread that can be used for darning or visible mending. Many brands of darning wool have quite a high percentage of synthetic fibre in them- so it’s worth checking before you buy and being sure of what you want!

I personally prefer to avoid synthetics, as they’re made from oil and will release microplastics in the wash. However, some people prefer these synthetic mixes for darning socks, as it makes them a little more hard wearing. As most socks are made with a percentage of synthetic fibre in them, you’ll often see them wearing down to that fibre before they get holes.  

All the darning yarns you’ll find on my website are pure natural fibres, with no synthetics.

 Comparing Hand Knitting Yarn to Darning Yarn 

As far as I can work out, 4ply (a UK hand knitting weight, nothing to do with the ply of the yarn at all) or Fingering weight hand knitting yarns are between 2/6 -2/8nm (or 1/3 -1-4nm). This is very approximate. So these are a lot thicker than the thickest darning yarn I sell, which is 2/14 (or 1/7)nm.

Lace weight yarn ranges from 1/6 - 1/11nm which are on the finer end and the 1/11nm is closer to the “fine darning wool” I sell, which is 1/14nm, and includes the thicker of my wools.

What is the best wool for darning and mending?  

The best wool for darning and visible mending is of course what’s going to work best with your garment. I always recommend matching the weight of the darning wool or yarn to the weight of the wool or yarn used in your knitwear. The closer the match is, the better it will work.

Try to match fibre type too, although this isn’t as important. Just be sure you can wash both the darning yarn and your garment safely in the same wash! Animal hair fibres like wool, cashmere, alpaca and mohair can all be fairly safely interchanged.  

If you’re not sure what weight of yarn your sweater is made from, judge it by eye.

I would recommend opting for what I call my “fine darning wool” or any pack of my cashmere yarn. These are all the same weight (1/14nm or 2/28nm) and most knitwear isn’t finer than this, so just choose the colours you like best!  

The great thing about opting for a very fine yarn, is that you can always double it up to make it thicker. This is something I often do, sometimes quadrupling the yarn or more depending on my mending project.

Darning Wool for Mending Merino Base Layers

Merino base layers however are much finer, and for these I would use my “Super Fine Merino Darning Wool” to mend them. The yarns in this darning wool set do vary slightly in thickness, from 2/60nm to 2/46nm. Most of it is 2/48nm. They’re pre-consumer waste yarns, and I’m working with what I have been able to get. I very rarely come across wool this fine- it’s a bit like sewing thread in thickness!

I do also have some thicker darning wool available, a 2/17nm thickness, which isn’t suitable for very fine knitwear, but is lovely for anything a bit heavier. Again, you can ply it up yourself if you need it to be thicker.  

The thickest wool I use for darning is 2/14nm (equivalent to 1/7nm so towards the heavier end of lace weight hand knitting yarns), and I only sell it as it as part of kits. The fabric I send out is made with this yarn so it’s an exact match, meaning you have the best chance to create a darn that comes out nicely if you opt to have one of my kits to practice with.

 What to do if you can’t find the right yarn for mending?

Despite this slightly technical post, I would urge you not to get too hung up on the exact weight of yarn for mending your knitwear, and work with what you can get or already have. It’s much better to get on with your mending project than leave it to get worse or just sit in your mending pile. You can always adjust your mending if your yarn is a bit too thick or a bit too thin.

In fact my latest repair project is one of those- my fine yarn is slightly too fine, and if I double it up it’s slightly too thick! In these situations, I normally go for the finer yarn option and just add in more rows as needed. It works out fine, and no one would know except me (and now you as I’ve shared this photo!).  

The joy of visible mending is that you can use yarns that are not an exact match, make a feature of that, and call it a design choice!