A knitting machine knits yarn automatically, after being set or programmed to knit a specific pattern. A knitting machine saves time compared to hand knitting, but the machine knitter must still pay close attention to the knitting machine as slipped or tangled stitches are common. Yarn thickness is the single most important consideration when choosing a knitting machine.

If the yarn used in a knitting machine is too thick, the hooks that hold and knit the yarn automatically will split right through the yarn. When choosing a knitting machine, the knitter must decide what kind of knitted items the machine will be used to make. There are three kinds of knitting machines: flat bed for lightweight items, mid gauge for mid-weight items, and bulky or chunky for heavy items.

A flat bed knitting machine has small hooks placed .45 centimeters (4.5mm) apart. These machines are good for Fairisle patterns, cables, and lace. Baby weight or sometimes even thinner yarn can be used. The thickest yarn that can usually be used on a flatbed knitting machine is sport or DK.

A mid gauge knitting machine produces garments that look the most like hand knitting. The hooks are placed .65 centimeters (6.5mm) apart. Sometimes baby weight or chunky yarns may be used, but not always. Common worsted, sport, and DK yarns usually work best, but check with the manufacturer's instructions.

A bulky or chunky knitting machine has hooks placed .9 centimeters (9mm) apart and is perfect for making heavy sweaters. Cables and Fairisle patterns usually work well. Sport or DK are the smallest weight of yarns that should be used on a bulky knitting machine, but will not work on some models. Bulky or chunky style yarns work best.

Although no knitting machine made so far can replicate every hand knitting stitch, a knitting machine is a fast, reliable way to knit products for home use or for sale. It is important to remember, however, that machine knitting is not necessarily easier than hand knitting. A knitting machine needs much more attention to detail than a sewing machine and can require regular untangling of caught yarn and pick-ups of slipped stitches.

Like hand knitting, sample swatches still need to be made for each pattern. Moreover, machine hook sizes do not coordinate with hand knitting needle sizes. Personal computer (PC) software is available to allow for custom knitting machine patterns. More expensive machines may do more stitches and handle more yarn at one time, but all knitting machines work well. The right machine for the right yarn is the key to choosing the best machine for every machine knitter.