I'm sure this happens to more people than just me- you look at your stash of yarn, complete with this mushy, half-used balls wound into an enticing menagerie of color and wonder what in the world to do with it all. I compulsively buy a little extra when I have a project in mind that I would like to knit, that way I'm ensured to have enough. However, once the project is done, there are the leftovers. And just like with food, it can be money saving, fun, and sometimes surprisingly tasty to use leftovers. Other times it can be lack luster, disappointing, and/or a little disgusting. I think my biggest fear of using one of those squishy, half-used balls of yarn in my stash is the mystery of whether or not I will have enough to complete my goal. Nobody wants to spend the hours knitting a project just to be short a few meters at the end. What if the yarn is discontinued and there is no hope of getting more?! With food, I often resort to the sniff test when questioning whether or not a leftover should be used. What's the sniff test for yarn?
Well, it turns out the answer to that is much more scientific (or rather, mathematic) than sniffing. I guess I should preface this with the statement that you should ALWAYS keep your ball band. (The ball band is the little bit of paper that you get on a ball or skein of yarn that has all that important information on it- like length, weight, needle suggestion, gauge, etc.) I love to shove the ball band in the middle of my yarn cakes so it stays put even when I move my yarn stash about. Even if you have a great memory, I doubt there are many people who can boast a memory great enough to keep track of the yards per grams for all of their yarn. Not saying it's impossible, just saying it is probably outside most of our spheres. There is still hope if your leftovers are lacking in ball bands. Please see note at the end of post.
All you need to get started in unraveling the mystery of how much yarn is left is a scale (any small kitchen scale will do), your yarn, a calculator or pencil and paper, and your yarn's ball band.
Once you turn your scale on, many kitchen scales boast a feature of being able to switch from ounces to grams. You will want to reference your ball band and see exactly how your length per weight is reported. If it is recorded in yards per grams, you will want to make sure your scale is set to grams. Likewise, if you have yards per ounces you will want the scale set to ounces. Whether your yarn is measure in meters or yards does not matter for this step, but is important to know for pattern reading purposes. (If you are not using a digital scale, you still need to pay attention to whether you are measuring in ounces or grams. There was life before digital things and you can even use a triple beam balance for this if you feel so inclined. I will not get into that here, but if you have a triple beam balance, I will assume you know how to use it.)
Make sure your scale is zeroed (For digital scales, the screen should not have any numbers but 0 on the readout. If your scale is reading out some numbers to you, you can zero your scale by pressing the "zero" button.) Then, place your yarn on the scale. If your yarn is in a higgilty piggilty mess, you can always place a bowl on the scale, zero your scale, then place the yarn in the bowl. (Or record the weight of your bowl when empty, add your yarn, record the value of the yarn and the bowl then subtract the weight of the bowl from the total, leaving only the weight of your yarn.) Read the number on your scale.
In my example, my yarn weighed 95 grams. I had used a small portion of this ball of yarn to knit a sample and ended up choosing a different yarn for the project. The critical question in my head was whether there was still enough yarn left in this ball to knit a pair of socks. The next thing I did was look at the ball band and find where my length per weight was recorded.
In this particular case, for this particular yarn, there are 462 yards/ 100 grams. Now it's time for a little algebra.
I know there are 462 yards per every 100 grams of this yarn, but I want to know how many yards I have left after my sampling. After measuring my current ball of yarn, I know I have 95 grams of my yarn left; how does that translate to yards?
Dividing 462 yards by 100 grams simplifies down to 4.62 yards per 1 gram. (I simply put 462 in my calculator and divided that number by 100.) I have 95 grams. I can now multiply my 95 grams by 4.62 yards/gram. (Again, I used my calculator. I typed 95 and multiplied it by 4.62.) The units of grams cancel and I am left with 438.9 yards. This lets me know that I have roughly 439 yards of my yarn leftover and can plan my project accordingly.
Here is an equation you can use if perhaps my example was a little confusing or not quite close enough to your numbers to be helpful. It should work for you whether your yarn is measured in meters or yards, grams or ounces.
length of leftover yarn= (length/weight recorded on ball band of yarn) x (measured weight of leftover yarn)
I hope this helps clear up some of those leftovers off your shelf and leads to some beautiful projects!
***For those leftovers lacking a ball band: It's a little trickier, but you can figure out the length per weight on your own. Using your scale and starting with the end of your yarn, make a little pile of the yarn on the scale until you get 1 gram or ounce. Mark your yarn where this occurs or use some scissors to snip the yarn. Measure the length of this piece of yarn. You should now have the desired length/weight to multiply by the measured weight of your leftovers. It's not perfect, but it'll get you pretty darn close.