A knitting chart is a visual representation of a knitting pattern. The chart shows which stitches need to be made and when, and if the pattern is multicolored, the chart also shows when and where colors need to be switched. This is in contrast with written knitting directions, which lack a visual component. Some knitters find it easier to work with a knitting chart, while others prefer written directions, and some people use both, depending on the project. Charts are especially useful for lace patterns and multicolored garments.
Reading a knitting chart can be a bit confusing, especially at first. All knitting charts start on the bottom right corner, and many omit the even rows, assuming that the knitter will be purling straight across (or alternating knit and purl stitches, when ribbing is involved). The knitter starts by casting on the required number of stitches, and then he or she follows the chart from right to left to the end of the row. If the chart includes even rows, the knitter then reads from left to right, ending up back on the right hand side of the pattern. If the even rows are left out, the knitter works the even row, and starts again on the right side with the third row, and so on, until the piece is complete.
As a general rule, a knitting chart is created on a grid, with each square of the grid representing a single stitch. Squares are typically left blank when the stitch is a simple knit stitch, so that the pattern does not become too confusing. Various symbols tell the knitter when to purl, create an increase, decrease stitches, and so forth, and the chart may also be color-coded, when a color pattern is being created.
Because a knitting chart can get very complex, it is usually accompanied with a key which explains what each symbol means. The chart also typically includes a gauge, telling the knitter how many stitches and rows fill a set area of space. The knitting gauge is very important with garments, because garments which are not knitted to gauge will not fit right. Most knitters working with unfamiliar yarn knit a test swatch before they start to make sure that they are working to gauge, and they may adjust the needle size or yarn to get the right gauge.
Knitting stores often carry knitting charts, sometimes with samples of completed items made using the chart so that knitters can decide whether or not they like the pattern. Knitters also exchange charts online, and some knitters like to write out patterns in chart form before they begin on projects they invent, to ensure that their knitting remains consistent throughout the project.