Knit fabric curls because of built-in tension in the structure of the stitches themselves, and the most reliable way to stop it depends on whether you’re hand-knitting a project or sewing with store-bought knit fabric. For knitters, choosing balanced stitch patterns or adding non-curling borders solves the problem at the source. For sewists, a combination of starching, stabilizing, and machine adjustments tames curling edges long enough to cut and sew clean seams.
Why Knit Fabric Curls in the First Place
Stockinette stitch, the smooth “V” pattern you see on most knit fabrics, is made of rows of interlocking loops where the yarn bends in one consistent direction. Each loop creates a tiny amount of torque, and when thousands of loops line up the same way, all that stored energy adds up. The fabric relieves that tension by rolling: side edges curl toward the front (the knit side), while the top and bottom edges curl toward the back (the purl side).
Research into the mechanics of knit curling confirms that the three-dimensional shape of each individual loop drives the behavior. Vertically elongated loops produce strong side curling. Horizontally elongated loops produce top-and-bottom curling. Most stockinette falls somewhere in between, producing the familiar “double curl” where all four edges roll. This is a structural property of the fabric, not a defect. You can’t permanently press it out with an iron alone because the yarn wants to return to its relaxed, curled state.
Stitch Patterns That Eliminate Curling
The reason stockinette curls and other patterns don’t comes down to balance. Stockinette has all knit stitches on one side and all purl stitches on the other, so the tension pulls in one direction. Patterns that mix knit and purl stitches on the same row, or alternate them row by row, cancel out those opposing forces and lay flat naturally.
The most common curl-free stitch patterns:
- Garter stitch: Knit every row. Produces a bumpy, squishy fabric that lies completely flat. Great for scarves and blankets.
- Seed stitch (moss stitch): Alternate knit and purl stitches across each row, offsetting them on the next row. Creates a textured, pebbly surface with zero curl.
- Ribbing: Columns of knit and purl stitches (like knit 1, purl 1 or knit 2, purl 2). Lies flat and pulls inward, which is why it’s the standard choice for cuffs and neckbands.
- Double stockinette: A lesser-known option that looks like stockinette on both sides. Because the structure is symmetrical, the forces balance out and the fabric doesn’t curl. It uses more yarn and creates a thicker fabric, but it’s the closest you can get to that smooth stockinette look without the rolling.
Adding Non-Curling Borders to Stockinette
If you want the body of your piece in stockinette, you can frame it with a border in a balanced stitch. A garter stitch border (knitting every row for the first and last several stitches, plus the first and last several rows) acts as a flat frame that holds the curling center in check. A seed stitch border works the same way and gives a more polished look.
The border needs to be wide enough to counteract the curl. A two-stitch border is rarely sufficient. Most knitters find that five to eight stitches on each side, and five to eight rows on the top and bottom, provide enough weight and structure to keep the edges from flipping. For a large piece like a blanket, you may need even more. The wider the stockinette panel, the stronger the curling force, so scale your border accordingly.
Starching Knit Fabric Before Cutting
If you’re sewing with purchased knit fabric (jersey, interlock, ponte), curling edges make cutting and pinning a nightmare. Starching the fabric before you cut is one of the most effective tricks for getting it to behave.
For lightweight cotton jersey that curls aggressively, a boiled cornstarch solution works better than commercial spray starch. Combine a quarter cup of cornstarch with two quarts of cold water in a pot, heating and stirring until it thickens and boils. Let it cool slightly, then submerge your pre-wetted fabric, swish it around, and wring it out. You can spin out the excess in your washing machine on a low spin cycle. Iron the fabric dry at a wool setting (around 300°F) to activate the starch without scorching it. Set the iron down and hold it for a few seconds in each spot, then rotate slightly before lifting, as the starched fabric can stick.
For smaller jobs, a quick spray starch works well enough. Shake one teaspoon of cornstarch into one cup of water in a spray bottle. Spray the edges or the full piece until damp, then press dry with an iron on the same wool setting. The starch washes out completely in the first laundry cycle, so this is purely a sewing aid, not a permanent fix. But it makes the fabric lie flat, accept pins, and feed through your machine smoothly.
Stabilizing Edges for Sewing
Once your fabric is cut, the raw edges will start curling again unless you stabilize them. Two products handle this well:
- Fusible knit interfacing: A lightweight iron-on material designed to add structure without eliminating stretch. Press a strip along necklines, hems, or any edge that needs to stay flat. It bonds permanently and survives washing.
- Bias stay tape: A narrow, slightly stretchy tape you fuse along shoulder seams, necklines, or waistbands to prevent them from stretching out or rolling. It stabilizes the edge while allowing the rest of the fabric to move naturally.
Both are applied with an iron before you sew the seam. For hems specifically, fusible tape or a strip of interfacing along the fold line keeps the edge from curling up while you stitch.
Machine Settings That Reduce Curling
Even with good preparation, knit fabric can stretch and wave as it passes through a sewing machine, creating new curling problems along finished seams. If you’re using a serger (overlocker), the differential feed setting is your most important tool.
At a setting of 1 (or “N” for normal), both sets of feed dogs move at the same speed. This works for woven fabrics but often stretches knits, leaving you with wavy, curled seam edges. Turning the differential feed to a higher number (like 1.5 or 2) feeds more fabric into the front feed dogs than the back ones, gently easing the fabric and preventing it from stretching as it’s sewn. The result is a flat, smooth seam.
Going in the opposite direction, a setting below 1, actually stretches the fabric on purpose. This is what creates those ruffled “lettuce edges” you see on some knit tops. If your seams are coming out wavy and you haven’t touched the differential feed, check that it hasn’t slipped below 1.
Because every knit fabric behaves differently, test your settings on a scrap piece first. Adjust the differential feed in small increments until the test seam lies flat with no waviness or puckering. The stitch length interacts with the differential feed, so changing one may require tweaking the other.
Blocking Finished Knit Projects
For hand-knit items, blocking after finishing is the traditional way to relax curling and set the fabric into shape. The method you choose depends on the fiber.
Wet blocking works for most natural fibers. Soak the finished piece in lukewarm water for 15 to 20 minutes, gently squeeze out the excess (never wring), and pin it to a blocking mat at the correct dimensions. Let it dry completely before unpinning. Wool responds especially well because the fibers relax and “remember” their new shape when they dry under tension. Cotton is heavier when wet, so use plenty of pins to keep the edges from sagging.
Steam blocking is faster. You hold a steam iron just above the surface of the fabric without pressing down, letting the steam penetrate and relax the fibers. This works well for wool and plant fibers. Avoid steam blocking acrylic yarn, as the heat can permanently alter the texture or even melt the fibers. For acrylic, wet blocking at room temperature is the safer choice.
Blocking can reduce curling significantly, especially in wool, but it won’t permanently flatten a pure stockinette piece with no border. The curling will gradually return as the fabric is worn and washed. Think of blocking as a reset that buys you time, not a one-time cure. For stockinette projects where flat edges matter, combining a balanced-stitch border with blocking gives you the best long-term results.