Sweater design is a specialization of fashion design in which knitted sweaters are designed to fulfill certain aesthetic, functional and commercial criteria. The designer typically considers factors such as the insulating power of the sweater (and its resulting warmth for the wearer); the fashion of its colors, patterns, silhouette and style lines, particularly the neckline and waistline; the convenience and practicality of its cut; and in commercial design, the cost of its production and the profitability of its price point. Sweater designs are often published in books and knitting magazines. Sweater design is an old art, but continues to attract new designers, such as Nicky Epstein and Meg Swansen.

The aim of sweater design is a sweater that fulfils certain criteria. The primary criterion is that its intended wearer wants to wear it and, in case of commercial sweater design, is willing to buy it at a commercially feasible price point. General secondary criteria include

To satisfy these secondary criteria, the designer has several tools at their disposal, such as yarns, colors, patterns, textures, necklines, hemlines, sleeve shapes, style lines, pockets and embellishments, as well as the fit of the garment to its intended wearer, the silhouette.

Despite the wealth of design techniques and studies of successful designs, the primary criterion (that the sweater be desired) is not always achieved, often due to factors beyond the designer's control including serendipity.

Sweaters are worn in various circumstances. For example, while some sweaters are worn at fancy dress occasions, others are worn to work, to religious services, in sporting or outdoors events such as hiking and camping. Similarly, the choice of a sweater can vary with different climates and different seasons, even with different times of the day. The sweater designer will generally target a particular occasion and temperature, e.g., a bulky, cabled, long-sleeved woolen seater for camping versus a refined, elegantly simple, short-sleeved cashmere sweater for white-collar work.

Comfort is paramount; the sweater should make the wearer feel at ease, in the most general sense. The temperature should be right, the fabric should "breathe" and should not irritate the skin. The sweater should hang right and not need constant adjustment; It should fit well and allow for customary motion without binding (e.g., at the armholes). Finally, a sweater should not make the wearer feel uncomfortable because of its "cut" (e.g. showing bra straps or too much cleavage) or general style (e.g., colors/patterns that the wearer feels are inappropriate).

The fit of a sweater affects its comfort, its attractiveness and, sometimes, its practicality (e.g., dangling sleeves can fall into food or get caught on hooks).

The simplest sweaters (drop sleeve, cylindrical) require six measurements: