This, and that, and do I have enough wool?

I'm still feeling a little swamped by work, though pleasantly so - things are coming up that might mean really interesting projects in the future, there's some progress on the writing front (though there's never, ever as much as I'd like) and I may have figured out a way to find out whether the yarn I have is enough for a knitting project.


A good while ago, a relative gifted me with her old knitting stuff - an assortment of yarns, and among that three packages that were once intended for a sweater, pullover, cardigan or whatever you might name it. Now due to a lot of different reasons (most of them related to shape - my shape), I am not going to knit a given sweater pattern as written. I prefer a zipper to a button band (I'm just not a button person), I am probably going to shorten the whole piece so the hem falls where I want it, I am also probably going to shorten the arms, and I might fiddle with other elements. And the size - I normally fall between sizes.

With all these alterations, though, and yarn that is not available anymore (and not listed in Ravelry), how am I going to figure out whether it is enough yarn for the project? There's lots of guidelines on how much one needs, but somehow I don't trust them.

So here's a different possibility (that I hope will work out well):
Knit a swatch. (You wanted to anyways, right?) This should be at least the typical swatch size, as in at least 12 x 12 cm (or 5 x 5 inch) to let you measure the gauge correctly (since that may be necessary knowledge for altering the pattern). Do whatever you plan to do with the finished piece - wash it, feed it to the dog, ... you know the drill. (At least theoretically, I'm sure you know it.)

Then you calculate the area in cm² that your swatch has. You might want to leave out the very edges to be on the safe side - so 11.5 x 11.5 cm on a swatch that actually measures 12 on each side. Then you put it onto a good kitchen scale - diet scale will be a good idea, probably. You now have two numbers.

Next, you can roughly calculate the area in cm² that your finished piece will have. A sweater will typically consist of one body (roughly a tube) and two sleeves (also roughly a tube). For these calculations, I just took the widest width of the body part and the total length to calculate the body surface area and the upper arm width and desired sleeve length to calculate the sleeve surface area. (Don't forget that you will need two sleeves!)

Now you can divide the complete sweater surface area by the swatch surface area. This tells you how many swatches would be equivalent to your sweater. Now you multiply the swatch weight by this number, and you get an approximate finished weight for the sweater. (Approximate because shaping, armholes and neckline are not considered.) Compare that to the weight of your available yarn... and if your yarn weight is greater or equal, you should be good to go.