Last Friday, we looked at swatching to match tension on flat knitting. What if the piece is knit in the round? Can we just assume the same tension for both? Here's the answer, at least for one knitter. This is a swatch knitted with the same yarn as the flat one last week, on 3.75mm and 4.00mm needles. It's made along the same lines: cast on enough to give five or six inches to measure across, work garter stitch for a few rounds, change to stocking stitch, and so on. The same time-saving strategem of making two swatches in one with a garter stitch division between them was used here too. You'd expect that the same knitter with the same yarn would get stitches of the same size, but that's not what happened. The 3.75mm needles gave 23 stitches to the inch in the round, but 22 to the inch knit flat. 4.00mm gave 22 stitches to the inch in the round, but 21 when knit flat. In other words, if this knitter were to swatch flat and then knit the garment in the round, the finished article would come out smaller than intended. So what's different about the two swatches? Same yarn, same knitter, remember? There's a clue in the fabric that was knitted flat. Here's a closer look at it: Those pictures show the stocking stitch and reverse stocking stitch sides of the swatch. See the way there are faint lines every couple of rows on the stocking stitch side, and how the purl bumps cluster in pairs on the reverse side? That's called rowing out, and it's what you get when you knit more loosely than you purl or vice versa, so that every second line is looser than the preceding one. While blocking will even up the odd loose stitch across a row, it won't fix rowing out, and if you're knitting with cotton, the lines will be even more noticeable. What's clear is that this knitter rows out. But when she knits in the round, she's not purling to get stocking stitch, so the difference between her knits and purls is irrelevant. Since it's her purls that are looser, the stitches overall are smaller, and so she gets a tighter fabric in the round. Sure enough, when you look closely, the telltale clumping is gone: Do you knit more loosely than you purl? One way to find out is to try swatching in the round - if your in-the-round tension comes out larger your knits are bigger than your purls; if it's smaller your purls are bigger than your knits. If you find you row out and you want to change this, then TECHknitter has an excellent post here addressing the issue. For the record, the knitter who made these swatches generally finds that using a needle one size down to purl in the flat works (interchangeable needles make this easy), though she knits in the round any chance she gets, thus avoiding the problem entirely.