Uneven knitting

In knitting, the word gauge is used both in hand knitting and machine knitting; the latter, technical abbreviation GG, refers to "Knitting Machines" fineness size. In both cases, the term refers to the number of stitches per inch, not the size of the finished garment. In both cases, the gauge is measured by counting the number of stitches (in hand knitting) or the number of needles (on a knitting machine bed) over several inches then dividing by the number of inches in the width of the sample.

There are two types of classification of Knitting Gauges or Unit of Measure:

Compared graduation scale Gauge (GG) A versus B system: A 30 GG (A) Cotton Fully fashion flat machine (30 needles in 1,5”) is comparable to a 20 GG (B) Electronic Flat machine, a 27 GG (A) is an 18 GG (B), an 18 GG (A) is a 12 GG (B), a 12 GG (A) is an 8 GG (B), a 7,5 GG (A) is a 5 GG (B) and a 4,5 GG (A) is a 3 GG (B).

The gauge of a knitted fabric depends on the pattern of stitches in the fabric, the kind of yarn, the size of knitting needles, and the tension of the individual knitter (i.e., how much yarn he or she allows between stitches).

Sometimes the gauge is deliberately altered within a garment, usually by changing needle size; for example, smaller stitches are often made at the collar, sleeve cuffs, hemline ribbing or pocket edges.

Uneven knitting is a knitting technique in which two knitting needles of different sizes are used. The method is sometimes used when the knitter has a significantly different gauge on knit and purl stitches. It is also useful for producing elongated stitches and certain specialty patterns.

To produce a knitted garment of given dimensions, whether from one's own design or from a published pattern, the gauge should match as closely as possible; significant differences in gauge will lead to a deformed garment. Patterns for knitting projects almost always include a suggested gauge for the project.

For illustration, suppose that a sweater is designed to measure 40" around the bustline with a gauge of 5 st/inch in the chosen stitch. Therefore, the pattern should call for 200 stitches (5 st/inch x 40") at the bustline. If the knitter follows the pattern with a gauge of 4 st/inch, the sweater will measure 50" around the bustline (200 st / 4st/in) -- too baggy! Conversely, if the knitter follows the pattern with a gauge of 6 st/inch, the sweater will measure ~33" around the bustline (200 st / 6st/inch) -- too tight! Generally, the gauge should match to better than 5%, corresponding to 1" of ease in a 20" width. Similar concerns apply to the number of rows per inch.

...
Wikipedia