This is the single most useful distinction in sewing, and it is invisible on a shop shelf until you know what to look for. Almost every “why did my seam break” and “why does my hem ripple” problem traces back to treating a knit like a woven.
The Structural Difference
Woven fabric is made of threads crossing at right angles — warp running the length, weft across. Think of a basket. The structure is stable and does not stretch along either thread direction. Cotton poplin, denim, linen, canvas and most quilting cotton are wovens.
Knit fabric is made of loops of yarn pulled through other loops, like hand knitting done very finely. Because loops can elongate and recover, the fabric stretches. Jersey, interlock, rib, French terry and most T-shirt fabric are knits.
How to Tell Them Apart
- Stretch it. Pull crosswise. A woven barely gives; a knit stretches noticeably and springs back.
- Look at a cut edge. Wovens fray into loose threads. Knits do not fray — they curl, usually towards the right side.
- Look closely at the surface. A woven shows a grid. A knit shows tiny V shapes on the front and horizontal loops on the back.
One useful exception: woven fabric does stretch on the bias — at 45 degrees to the threads. That is exactly why bias binding works and why bias-cut garments drape as they do.
Sewing Wovens
Wovens are the forgiving option and the reason beginners are usually pointed at cotton.
- Needle: universal or sharp/microtex. See needle sizes and types.
- Stitch: plain straight stitch, around 2.5 mm. See what stitch length to use.
- Edges: will fray, so finish them — zigzag, overcast, pinking or a serger.
Sewing Knits
Knits need three changes, and skipping any one of them causes a specific, recognisable failure.
1. Use a ballpoint or stretch needle
A sharp needle pierces the loops that make up the fabric, cutting them. The damage often does not show immediately — it appears as a run or small holes along the seam after a wash or two. A ballpoint pushes between the loops instead.
2. Use a stitch that stretches
This is the one people miss. A straight stitch has no give. When the wearer moves and the fabric stretches, the thread cannot, so it snaps — the classic popped shoulder seam.
Use a narrow zigzag (roughly 0.5–1 mm wide, 2.5 mm long), or your machine’s dedicated stretch or lightning-bolt stitch if it has one. For hems, a twin needle produces two parallel lines on top and a zigzag underneath, which stretches.
3. Do not stretch the fabric as you sew
Let the machine feed it. Pulling produces a wavy, stretched-out seam that never recovers. A walking foot helps considerably here, and reducing presser foot pressure helps if your machine allows it.
Common Failures and What Caused Them
- Seam pops when worn — straight stitch on a knit. Use a stretch stitch.
- Small holes along the seam — sharp needle on a knit. Use ballpoint.
- Wavy, rippled hem — fabric stretched while sewing. Slow down, use a walking foot.
- Skipped stitches on jersey — wrong needle type, most often. Change before touching tension.
- Edges curling while cutting — normal for knit. Cut with the fabric flat and use plenty of weight, or spray starch it first.
Which Should a Beginner Start With?
Wovens, comfortably. They sit still, they cut accurately, and an ordinary straight stitch works. Knits are not difficult once you know the three rules above, but learning them at the same time as learning the machine makes everything harder than it needs to be.
If you do want to sew knits regularly, a serger is the single biggest upgrade available — the stitch it produces is inherently stretchy and finishes the edge at the same time.
