Long tail cast on

I posted this question before and got an answer, but I cannot find it now! Anyway, the question was is there an easier way to do the long tail cast on without having to guess at how long the tail should be?

Estimating how long you need comes with experience. If you have to cast on lots and lots of sts, some people use 2 ends of yarn - one for the thumb, the other over the fingers. I usually find that a yard makes about 40 sts which includes about 3-5" for a tail.

Thanks suzeeq! I found my original post! Jan from CA posted this:
The easiest way to do it for that many stitches is to use two skeins or the yarn from the outside and inside of the ball. - If you normally use a slip knot just tie a slip knot with both strands and put your needle through it. Then you use the two strands to cast on (one over thumb, one over fingers) and when you have enough stitches just cut the yarn from the end you don’t want to knit with and weave that in later. You never run out of tail with this method.

Yep, some people do that for all but a small amount of stitches, some when they need more than 100 or some when they need 200 or more. If I do more than 150 I usually just use a cable or knit CO because I don’t like to cut yarn or deal with more ends than I have to.

I wrap the yarn around both needles (to give me a little leeway) as many times as the stitches I need. When you get to, say, 150, that’s whereyou put the slipknot. Some people only wrap one needle, but somehow I always come up short. Using both gives me enough and a little extra, which is better than not quite enough.

See, if I did that I’d come out with twice as much tail as I need. The tail yarn doesn’t go around the needle when you cast on, but around the loop that’s on the needle. So it doesn’t take as much yarn as the loop on the needle.

Here’s a video that shows you how to cast on with two balls of yarn and no waste.