If you’re a mathphobe, be warned. There’s gonna be a lot of math in this one.

Because I’ve got a pile of yarn and a plan. But not too much of a plan, because obviously that wouldn’t be fun.

So, I’m making a blanket- with a largeish gauge (I’m using US9s) in a lace pattern that I found… somewhere on the internet at some point in the past. I know that’s not great, and I would love to cite the original designer, but I literally have no information, except that it was a charted Japanese stitch pattern, probably from a stitch dictionary. Which one? I have no idea. (If you recognize it, please let me know and I’ll happily share the source.)

Anyway, I worked up a decent-sized swatch, I know I’m going to do this all-over lace pattern with a simple garter border, and I have a big pile of yarn. But how many repeats to cast on?

I could just guess, but that never ends well. Either I end up with a weirdly small blanket or I run out of yarn halfway through a king-size monstrosity. I’m aiming for a nice throw blanket this time. Big enough that the newlyweds can snuggle underneath it, but not so big that they will be celebrating their silver anniversary before it’s done.

I grabbed some tools. A pad and pen (I’m still old-school when it comes to math), a tape measure and my trusty kitchen scale.

First, I weighed the swatch: 30 grams. (I’ve got 12 skeins of 100 grams each, so 1200 grams of wool to work with.)

Then I measured the swatch. The whole blocked swatch was about 7.5x 9 inches, or 67 square inches.

So if 30g=67 square inches, I can do a little math to figure out that I can use my 1200g to work about 2680 square inches.

Then the next question is, If I have 2680 square inches to play with, how wide should the blanket be? In my head, the blanket is about 50 inches square… ish.

So I divided 2680 by 50, leaving me with 53.6. So, if I cast on 50″ across, I’ll have enough yarn for a 53″ long blanket.

Each repeat is about 3″ across, plus an inch and a half for each border, so dividing it out, that will give me 16.16. But, of course I can’t do part of a repeat, so I’ll round down to 16.

So to get my stitch count, I’ve got 6 stitches for the edges, plus 14 x 16 (14 stitches per repeat, 16 repeats), which gives me 230 stitches.

So now I’m off to cast on and cross my fingers that I did my math right!