|The project in question.|
Yesterday I posted about a new project I started and how I hoped I had enough yarn. Debbie from No Spring Chicken asked if there was a way to know ahead of time if we have enough when using stash yarn that we only have a certain amount of (rather than buying enough for the pattern).
Well, there's a few ways to do it. This is kind of math heavy so I'll try to explain it as simply as possible so those with Arithmaphobia (I'm looking at you Allison! ;) ) won't run away screaming.
Both methods involve a scale that can get down to an ounce/gram.
If you have yarn with the ball bands attached, or you can find the information needed via another source (Like Ravelry's yarn search) then this is the easiest method.
Most ball bands will tell you the weight and yardage of the skein. To figure out how many yards are in one ounce/gram divide the length by the weight.
225 yards/4 oz = 56.25 yards per oz
225 yards/50 grams = 4.5 yards per gram
Now, weigh the yarn you have. Let's use the yarn for my project as an example.
A full ball weighs 140 grams. (I prefer to weigh in grams, as I find it a bit more accurate.) I had already used a bit for a dish cloth, but I didn't weigh it before this project so let's just say I have 130 grams to start with. The full ball had 236 yards.
So, 236/140 equals 1.69 yards per gram. If I have 130 grams of yarn, then I have approximately 219.7 yards of yarn. Now I would compare this number to the yardage required in the pattern. That is, if I were using the same weight yarn. Which I'm not. It calls for DK and I'm using worsted, so I'm pretty much screwed but let's move on!
Let's say you don't have access to the information that is weight and yardage. You've misplaced the ball band. Or it's been 5 years since you last looked at the yarn after buying it at the yarn shop because you needed it RIGHT THEN even though you didn't have a project in mind, so it got pushed to the back of the closet and wild creatures have eaten the band and you really can't remember what the name of the yarn is, let alone the particulars.
Take a measure of yarn, say a yard or two (three would actually be best, just to be safe). And cut it from the ball. If you can't bring yourself to do this - I don't think I could either - you could just lay the measured portion on the scale, and put the attached ball to the side. It won't be as accurate, but it'll be good enough for those of us that don't like abusing yarn.
Either way (whole or cut) put the piece on the scale. From here you will know that three yards = X grams (or ounces, if you can get fractions). Do the same math as above:
(3 yards = 2 grams)
3 yards/2 grams = 1.50 yards per gram
Ball weighs 49 grams
49 (grams) x 1.50 (yards) = 73.5 yards total
Again, compare this information to your pattern, assuming you're using the same weight of yarn. If you're not using a pattern and are just going by ear not knowing how much you'll need total, well... May the Knitting Forces smile upon you.
Remember that if the pattern calls for a certain yardage make sure you have at LEAST 10% more than that to account for tension differences, starting and stopping new balls, seaming, etc.
I'm sure there are other ways to know how much yardage you have, but the first method is the one I've used for a few years now and it hasn't failed me yet. Unless of course I'm using a different yarn weight.