When it comes to cast on technique, this one, is my favorite, hands down. Borrowed from machine knitting, the Folded Method of Tubular cast on is versatile, easy to perform and just looks good!
Let's start with the version of this method for even number of stitches.
1. First of all, we need to provisionally cast on HALF the final number of stitches, so if you need to end up with 40 stitches, cast on 20. You may use any kind of provisional cast on technique, I usually use the Crochet Chain cast on.
With smooth, contrasting waste yarn and crochet hook, make a loose chain of about four stitches more than you need to cast on. Cut yarn and pull tail through last chain to secure. With needle, working yarn, and beginning two stitches from last chain worked, pick up and knit one stitch through the back loop of each chain for desired number of stitches.
No we have 1 row of working yarn loops on needle. Do not join in the round.
2. Purl 1 row. Knit 1 row. Purl 1 row.
3. Carefully remove the waste yarn and place the cast-on stitches onto a spare needle,
ending with the half loop at the edge of the fabric.
Make sure you have the same number of stitches on each needle.
4. Now bring the needle with the cast-on stitches up behind the working needle, with wrong sides together and work in knit 1, purl 1 rib as follows:
Next Row (RS): *Knit 1 from front needle, purl 1 from back needle; repeat from * to end.
The result is nice and neat edge which looks identical from both sides.
With even number of stitches, this method is works best for in-the-round projects, because it starts with knit stitch and ends with purl stitch.
See the folded Tubular Cast On looks on the brim of my Buoy Hat.
This method also works well over an odd number of stitches for the projects that worked flat.
In order to calculate the number of stitches for initial cast on, add one to the final number of stitches desired and divide that number by two.
For example, we need to end up with 53 stitches. (53+1)/2 = 27 stitches.
Now we need to work as for an even number of stitches, but when removing the waste yarn, don’t pick up the last half loop at the edge of the fabric; there will be one stitch fewer on the back needle than on the front.
Work in knit 1, purl 1 rib as follows: Row 1 (RS): *Knit 1 from front needle, purl 1 from back needle; repeat from * to last stitch, knit 1 from front needle. Row 2 (WS): *Purl 1, knit 1; repeat from * to last stitch, purl 1.