Most sock knitters have a preference when it comes to what kind of needles they use, whether it be four or five double-pointed needles or one or two circular needles. Every pattern, likewise, is written for a certain type and configuration of needle.
But that doesn't mean you're stuck working with circulars if you prefer double points. It's actually pretty easy to convert sock patterns for different configurations of needles; you just need to think about how the sock sits on the needles and what a particular pattern is telling you to do.
For the purposes of this article we're going to be thinking about cuff-down socks, but the same rules apply when converting toe-up patterns as well.
Understanding the Pattern
Think about a standard sock pattern, like my Women's Stockinette Stitch Sock. That pattern was written for five double-pointed needles, with a quarter of the stitches on each of four needles and the fifth used for the knitting.
That means two needles hold the front of the leg and two hold the back. The heel would then be worked across half the stitches, or two needles. The gusset is then picked up on those two needles with the remaining heel stitches, while the top of the foot sits on the other two needles.
In this particular pattern, the beginning of the round stays at the side of the foot throughout, so the first two needles are the top of the foot, where no shaping is happening. The shaping here happens on needles three and four for the gusset, then on every needle for the toe.
Changing Needle Type
Knowing all this information we can easily convert this pattern to be worked on two circular needles. Half of the stitches go on each needle: one for the front of the leg and one for the back. Work the heel on one needle, and pick up stitches for the gusset with the same needle. Your decreasing for the gusset will happen at each end of the needle with the heel stitches, while the stitches on the other needle are worked plain. And toe shaping will happen at each end of each needle.
If you want to knit the sock on one needle, again half of the stitches will be used for the heel and you'll decrease at each end of those stitches for the gusset.
You can also work this or any other sock pattern on four double-pointed needles instead of five; just put all of the stitches for the front of the leg and top of the foot onto one needle. In the case of this pattern, needles 1 and 2 are your needle 1, needle 3 in the pattern is your needle 2, and needle 4 in the pattern is your needle 3.
If you wanted to convert a pattern from circular needles to double-points, it's again just a matter of thinking about where things happen in the pattern and how you want your stitches to be divided. You can either divide the stitches into four even sections or put half of the stitches on one needle and divide the other half onto two needles.
When you get to the instructions for the heel in the pattern, work it on the two needles that have half the stitches on them if you're working with four needles, or with the first two needles if you have five. If there's gusset shaping, it's happening on the same needles that you worked your heel on; you'll probably either continue in the leg pattern on the other needle or needles or switch to Stockinette.
All of this may seem a little confusing in the abstract, but as you read and knit along with a pattern it becomes a lot clearer that as long as you understand which stitches are in play it doesn't matter what kind of needles you use.