I'm making one at the moment. I'm using 12mm needles and a wool that says its suitable for that size, so it's pretty thick and chunky. I cast on 20 stitches, which has resulted in about a 20cm wide scarf. I was after a wide, chunky scarf and I'm about half way through. It looks good, and the width is just right. I'd just keep on casting on until you think it looks right... but more than ten definitely!
As a guide though, look at the ball band on your yarn. It should give information about gauge/tension. It'll probably be a little diagram showing how many stitches you get to 10cm using a certain size of needle. This varies from person to person, depending on how tightly you need but should give you a clue about how many stitches to cast on to get the required size.
I've settled for 20 now, I realised that the width gets bigger than it looks on cast-on
My wool says to use 9mm needles, I'm using ten as the womanin the shop said it'd make a less blocked effect and I don't want it to look too heavy iykwim?
And borntofolk, thank you! I wondered what that diagram was! (somewhat a newbie knitter! ) 10 sticthes = 10cm apparently, and it looks about 20cm atm
This is my first project after constantly trying out squares and lines for practicing my casting on/off and purling methods, so I'm excited to see how this scarf continues! It's all knit (the lady in the shop said that purling would make it curl?) and it looks like it'll be quite chunky so far, a bit chunkier than I thought it would be but still lovely