Knitted fabric is a textile made by interlocking loops of yarn, as opposed to weaving, which crosses threads over and under each other in a grid. That looped structure is what gives knits their signature stretch and flexibility. Every t-shirt, pair of socks, and sweater in your closet is almost certainly knitted, and the same basic principle of interconnected loops applies to all of them, whether they’re made by hand or on an industrial machine.
How Loops Create Fabric
The core idea behind knitting is simple: a single yarn (or set of yarns) is bent into a series of loops, and each new loop is pulled through the one before it. Those loops lock together to form a continuous, flexible sheet. Unlike woven fabric, where straight threads are held rigid by crossing over and under one another, the curved loops in a knit can open and close. That’s why you can pull a knitted shirt sideways and it springs back, while a woven dress shirt barely stretches at all.
The loops run in two directions. Horizontal rows of stitches are called courses, and vertical columns are called wales. The number of courses and wales packed into a given area determines the fabric’s density, or gauge. Gauge is typically measured over a 4-inch (10 cm) square. A tighter gauge means more loops per inch, producing a denser, heavier fabric. A looser gauge creates a lighter, more open material. Getting gauge right matters enormously in garment production: even a small deviation in course count can make a sweater come out several inches too short or too long.
Weft Knitting vs. Warp Knitting
All knitted fabrics fall into one of two broad categories based on the direction the yarn travels.
Weft knitting uses a single yarn that moves horizontally, forming one row of loops at a time. Each new row builds on the previous one. This is the type of knitting you’d recognize from hand knitting with needles, and it’s also how most t-shirts and casual knitwear are made industrially. The single-yarn feed keeps production costs low and makes the fabric extremely flexible and stretchy. The tradeoff is that if a loop breaks, the fabric can “run,” unraveling along a column of wales the way a ladder runs through a stocking.
Warp knitting feeds many individual yarns simultaneously, each running roughly vertically and interlocking with its neighbors. The result is a more dimensionally stable fabric that resists runs. Tricot is the most common warp knit used in clothing, found in underwear, sportswear, and lingerie. Raschel knitting, another warp technique, produces open, lace-like structures and netting. Warp knits also show up in non-clothing products like car seat covers, where shape stability and durability matter more than stretch.
Common Types of Knitted Fabric
Within those two categories, a handful of stitch patterns account for most of the knitted fabric you encounter. All of them are built from just four basic stitches: the knit (plain) stitch, the purl (reverse knit) stitch, the missed stitch (which creates a small float of yarn on the back), and the tuck stitch (which creates an open space).
- Jersey (stockinette): The most common knit fabric. It uses plain stitches on the front and purl stitches on the back, giving it a smooth face and a slightly textured reverse. Your basic t-shirt is jersey. It’s lightweight and drapes well, but it curls at the edges, a natural result of the three-dimensional curve each loop takes through the fabric.
- Rib knit: Alternates columns of knit and purl stitches, creating vertical ridges. Rib fabric stretches dramatically widthwise, up to 170% in testing, making it ideal for cuffs, waistbands, and necklines. It also recovers well lengthwise, snapping back close to its original shape.
- Interlock: Essentially two layers of rib knit locked together. It’s thicker, smoother on both sides, and more stable than single jersey. Common in polo shirts and higher-end basics.
- French terry: Smooth on the outside with soft loops on the inside. This is the classic sweatshirt fabric, designed to trap warm air against the skin.
How Knits Differ From Woven Fabrics
The looped structure of knits gives them a fundamentally different set of properties compared to wovens. Stretch is the most obvious difference. Even without any spandex blended in, a knitted fabric stretches in multiple directions simply because the loops can deform and redistribute. Woven fabrics only stretch meaningfully on the diagonal (the bias) unless elastic fibers are added.
Knits also resist wrinkling better than most wovens because the loops absorb compression without creasing. They drape more fluidly and conform to the body, which is why activewear is almost always knitted. On the other hand, knits are less dimensionally stable. They can shrink 5 to 10% after washing, and over time they’re more prone to sagging and losing shape than a comparable woven fabric. Wovens hold their structure longer, which is why they’re preferred for tailored garments like dress shirts and suit jackets.
One practical difference for sewing: woven fabrics fray at cut edges because the loose thread ends unravel. Knits don’t fray the same way, but they can curl or run, depending on the stitch type.
Machines That Make Knitted Fabric
Industrial knitting happens on two main types of machines. Circular knitting machines have needles arranged in a cylinder and produce fabric as a continuous tube. Most t-shirt jersey, underwear, and hosiery comes off circular machines. The tube is either cut open and laid flat, or in the case of socks and seamless garments, used as-is with minimal sewing.
Flatbed knitting machines have two flat beds of needles arranged in a V shape. They’re used for heavier knits like sweaters and for shaped components like polo collars. The key advantage of flatbed machines is that they can shape panels to size during knitting itself, reducing the need to cut fabric afterward. Whole-garment knitting, where a complete sweater or dress comes off a single flatbed machine with almost no seams, is increasingly common in higher-end production.
Why Fiber Choice Matters in Knits
The yarn you choose changes how a knitted fabric performs, sometimes dramatically. Wool has high natural elasticity, stretching significantly and returning to its original shape, which makes it a natural fit for knitted garments. But wool fibers aren’t especially strong on their own, so wool socks are typically blended with nylon to survive repeated wear.
Cotton knits are soft, breathable, and comfortable against skin, which is why cotton jersey dominates casual clothing. Cotton has less natural stretch recovery than wool, though, so cotton knits are more likely to bag out at the elbows and knees over time. Synthetic fibers like polyester bring durability and moisture-wicking properties, making them the backbone of performance sportswear. Blending fibers lets manufacturers balance these strengths: a cotton-polyester jersey resists shrinkage better than pure cotton, while a wool-nylon sock lasts longer than pure wool.
Knits Beyond Clothing
Knitted fabrics have moved well beyond sweaters and socks. In medicine, knitted structures are used for implantable devices like hernia patches and cardiac repair patches. The porous, looped structure turns out to be well suited for drug delivery: medications can be loaded into the gaps between loops and released in response to body temperature or pH changes. Compression garments for managing circulation issues, from gloves to full bandages, rely on the controlled stretch that knitting provides.
In automotive manufacturing, warp-knit fabrics cover car seats because they hold their shape under daily stress. Sporting goods use engineered knits for everything from shoe uppers to protective padding, taking advantage of the ability to vary stitch density across a single piece of fabric, making it stiffer where support is needed and more flexible where movement matters.