A couple of months ago, I attended a Fibre Mart at the local weaver’s guild.  As always seems to happen, I came home with way more than I’d planned on but I also came home with a couple of unlabelled skeins of things.

Like these ones.

I can tell based on the feel, shininess,  drape, “squeakiness” and how it sticks to my dry hands that it’s likely a silk yarn but I can’t use it before I know how much yardage I have. In general, a wraps per inch (WPI) measurement and more specifically maybe even a grist would also be helpful.

A friend has started referring to me as a technical spinner and a technical knitter, so what the heck – let’s embrace this just for a moment.

No wait!  Come back!

Lots of people try to avoid the math but I find it’s really helpful for planning a project.  Since I started doing the (really very simple) math, I’ve not run out of yarn before the end of a project. Except for weaving calculations and I’ve finally figured out why I was doing that.

Knowing how to figure out the length and weight (i.e. 2/8, fingering, etc) of a skein is a great skill for unknown skeins who’ve lost their ball bands, yarn you’ve just spun or even leftovers once a project is finished.  The grist can help you figure out if one yarn is a good substitute for another.

Let’s look back at the skeins I showed earlier.  Here’s what else I  know about them:

• Each skein is 65g. (Or 2.32 oz ( 65g/28grams in an ounce) but grams will be more accurate for this particular calculation)
• I have 2 of them and a small portion of a 3rd.

Let’s see what else we can learn about it.  To get the numbers we need to figure out length and grist, we need to do only 3-4 steps:

1. Remove yarn from the niddy noddy or anything else that’s holding it under tension. This is important so you don’t end up with an overly high yardage that will just end in disappointment if you try to use all of it.  Why? Yarn under tension is longer than when it isn’t under tension.  Many of my wool yarns come off my 2 yard niddy noddy and immediately shrink to around 68″.  That’s more than 5% of the length.
2. If this is freshly spun yarn – set the twist and let it dry fully.  Why? It will change length. Sometimes only a little but sometimes as with crimpy wools, it can be upwards of 10%.  This 10% combined with the 5+% from removing it from the niddy noddy can mean 15% loss in total length. That’s significant.
3. Lay the skein on a flat surface. Measure the skein in its relaxed state. You can either go all the way around the skein (circumference), or measure the length of the skein like I did here and multiply this number by 2. My example skein is 23″ long and I’ll multiply that by 2 because I measured the length, not the circumference. So 46″. 
4. Count the wraps. This is the part that takes the time. My example skein is 792 wraps. (my partial skein is 27 wraps)

Now we have enough information to calculate the yardage and the grist of this yarn. That and wraps per inch (WPI) will give us pretty much everything we’d need to know about this yarn in order to use it in a project.

(For a good explanation of how to measure WPI, see here: https://spinoffmagazine.com/wraps-per-inch-by-amanda-berka )

Length/Yardage

So that formula then is:

wraps in the skein X total length of the skein = inches in the skein.

Then

Inches in the skein / 36 = yds in the skein

Let’s find the length first.

The first formula looks like this:

792 wraps X 46″ = 36,432 inches.

Inches in the skein / 36 = yds in the skein looks like this:

36,432 / 36 = 1012yds.

We can also combine the 2 formulas to look like this:

wraps in the skein X total length of the skein / 36 = yds in the skein

792 wraps X 46″ /  36 = 1012yds in each skein

If we want meters, we’ll divide that 36, 432 by 39.25, which gives us 928.2m (but for this calculation, we’ll use the yds measurement).

Based on this calculation, my partial skein will be 34.5 yds. (27 wraps X 46″ / 36)

Grist

Next, let’s find the grist or yards per pound. In general, as with Wraps Per Inch, the larger the number – the thinner the yarn.  In simple terms, grist is basically a way to represent the diameter and the density of the yarn combined.

This is most useful if you’re trying to match another yarn’s characteristics. For instance, if the yarn for a pattern is discontinued and you want to use another equivalent yarn.  It’s also really helpful if you’re trying to recreate one of your own yarns as a spinner or if you’re trying to make a yarn that will work as a substitute to a known yarn. (Note: the 453.592 is the number or grams in a pound)

To find grist, the formula is:
# of yards / # of grams x 453.592 = YPP

So our example skein is:
1012 yards / 65 grams  X 453.592 = 7,062.078 yards per pound.

Yes I know we’re switching back and forth from metric to imperial. I’m a Canadian of a certain age. I’m mathematically bilingual and mathematically confused at the same time.

Note: The Meters per Kilogram is actually an easier calculation in my mind but it’s YPP that we most often see on yarn charts, including the ones I’ll link to later in this post so we’ll use YPP.

So what do I now know about these skeins?
I have 133g in 2 and a bit skeins of this fibre.
That’s 2058.5 yds or 1888.04 m. (Not bad for $3!)
It has a grist of 7,062.078 ypp.
That’s firmly in light lace territory.
As a silk yarn, it should also be strong enough to weave with.

If I wanted to knit a pattern that for instance used a yarn that was 4000 ypp, I may find that this yarn would end up needing a very different needle size to get gauge, or might be unsuitable.  Differing grists in the same pattern on the same needles can be the difference between a light shawl and something that feels stifling or a lovely drape vs a stiff fabric. Conversely, if you’re looking for a towel with a firm hand and use something with a much higher YPP, you may end up with a sleazy fabric that isn’t resistant to wear at all instead. If you match the grist of the yarn used in the original pattern or at least come within about 1-200 ypp – you’ll more than likely come up with a finished item that’s very close to what the designer envisioned.

I could also consult the master yarn chart here: https://handwovenmagazine.com/master-yarn-chart/ to get an idea of a starting sett if I wanted to weave with it (somewhere around 36 EPI for plain weave), or a suitable yarn to pair it with – like a 28/2 wool yarn would be a similar grist.

As an additional bonus, if I know the grist of my yarn (calculated from the formulas above using my own measurements or what was on the original ball band) I can also figure out how much leftover yarn I have at the end of the project.  (This calculation will also work for leftover yarn on a cone – all you’d do is subtract the weight of the cone if you know it.  If you don’t – subtract maybe 10g for a small cone and 20g for a large cone to get a ballpark number.)

(Ypp / 453.592) * grams = yds leftover

So, we now that the YPP for this silk yarn is 7,062.078.

We also know that the partial skein is 3g.  That gives us enough information to work out how many yards I have in the partial skein.

Let’s try it:

(7,062.078/453.592) X 3

or

15.57 X 3 = 46.71 yds

Wait.  Didn’t I say above that my partial skein was 34.5yds?

This is likely as much a function of the accuracy of my scale as anything.  The truth will lie somewhere in the middle – and likely closer to the 34.5yds since it doesn’t rely on an accurate scale.  The larger the skein or partial skein, the less it will be subject to scale inaccuracies.

or let’s say this leftover was on a cone that weighed 8g:

(Ypp / 453.592) * (grams-cone weight) = yds leftover

(7,062.078/453.592)*(11-8)

or

15.57 X 3 = 46.71 yds

Just for fun, I decided to do a rough physical measure of this partial skein.  37.28yds.  This means that this partial skein is closer to 2.4g than 3g.  My scale only claims accuracy to within 1g, so this is very likely.

OK, that’s enough math for today.  I’m going to go prep some fibre and do some spinning.

Today’s post title comes from Joe Bonamassa’s Time Clocks album.  The song: Known Unknowns