Hello everyone. I’m new to knitting and I’m just finishing up my first project…a baby blanket for my niece. The blanket is 36inches wide and I’m wondering how much yarn I need to cast/bind off. I read that when changing yarn balls you’re supposed to be able to go the width of whatever you’re making 4 times for one row…I checked and the yarn I have left goes the width of the blanket 6 times. The blanket is 3 colors and the first 2 are about 12 inches long, but the final color for some reason ended up a few inches shorter (even though it’s the same size skein). Do I have enough yarn to do one more row or am I better off just casting off with the amount of yarn I have left? Any assistance is appreciated. 
How much yarn is needed for casting off?
The ‘4 times the width of one row’ rule depends a lot on what needle size you’re using. A large needle will take more than a smaller one. It’s a lot more accurate to figure out how much it takes to actually work one row, then you need about 1½ times that for the BO because it should be a little looser than when you work the row. I’d say bind off now, you probably don’t have enough to do a row and BO. Better to have a couple yards over than 12" too little.
Thanks! That was actually what I was worried about that I would run out of yarn, but I thought it would be better to ask somebody that knows more about knitting. I guess I should have mentioned that I’m using 10inch rounded needles before though. I just hated to waste yarn since I’m already short with this color to begin with. Thanks so much for your help!