How do I know how much wool I need to knit a scarf?

Question

If the wool says there is 78m per 50g ball and knits on 6.5mm needles with tension 14 stitches to 19 rows then how many square cm or inches will that produce?

I want to knit a scarf for my Nana for Christmas probably about 15cm/6inches wide and 150cm/60inches long.

I can't afford to buy more wool than I need so how many balls do I need?

It would be really useful if someone could explain how it figure it out rather than just give me an answer as I haven't chosen for definite my wool yet and lots of the others I'm considering are worked on different size needles with different tension.

Answer 1

Best Answer - Chosen by Asker

Perhaps you should select the pattern first. Patterns usually give you the yarn requirements for completing them.

The yarn you have selected is a bulky weight (Cat 5). From years of experience, I'm going to guesstimate that you can knit a scarf of about those dimensions in rib or mistake-stitch rib with four 50g balls of yarn. If you are dealing with a yarn shop (not a chain store), usually the owner will accommodate you in one of two ways: (1) You buy 5 balls and if it takes only 4, you can return the 5th ball within a time limit (60 days, 90 days). (2) You buy 4 balls and the owner puts the 5th ball aside for you. If you need it, you come in and buy it. If you don't, the owner returns the 5th ball to stock. You should know quickly if 4 balls is enough; knit 1 ball and measure the scarf so far, then multiply by 4 to get the length after 4 balls have been knit.

Finally, the way to be absolutely sure of the amount of yarn to buy is to buy one ball and then cast-on for the pattern you intend to knit. Let's say you cast on for a 6" width. Knit 4". You will have a 6" x 4" rectangle. Unravel the stitches and measure the yarn used. You will then know how many meters of yarn for 4 inches of scarf . Your desired length of 60" / 4" = 15 four-inch segments, so multiply the number of meters 4" takes by 15. Then you will know how many meters the scarf will take. Divide the total number of meters the scarf takes by 78 to get the number of balls. You'd round fractions UP unless they are tiny and you're willing to sacrifice some length to use fewer balls of yarn.

Example:

I cast on 21 stitches and knit 4" in mistake-stitch rib. I unravel the yarn and measure from the first cast-on stitch to the last knit stitch and find that I have used 20 meters. Do the math:

24 in sq = 20 meters of yarn
20 meters = 1/15 of the total (60" / 4" = 15 segments)
20 meters x 15 = 300 meters total
300 meters total / 78 meters per ball = 3.85 balls: buy 4 balls

I cast on 21 stitches on a larger needle and knit 4" in mistake-stitch rib. I unravel the yarn and measure. I've used 23 meters. Do the math:

24 in sq = 23 meters of yarn
23 meters = 1/15 of the total
23 meters x 15 = 345 meters total
345 meters total / 78 meters per ball = 4.42 balls: buy 5 balls

If the division yields a figure such as 4.02, though, you might decide to buy 4 balls and stop a bit short of 60"

Asker's Rating:

Asker's Comment:

Thank you. that's a really comprehensive answer. My problem is that I have to buy the wool off the internet as my local shops are useless, which means that the knit, unravel and measure part isn't really possible. You've been really helpful though so thank you.