It is important to know whether a throw will barely cover your lap or could easily cover a compact car. It is even more important to know whether a sweater will actually fit you. Most patterns include Size and/or Finished Measurement sections to indicate the expected dimensions of the finished piece.
Sizes are specified in very general terms, such as S (small), 1X (extra large), and 0-6 months. Finished measurements are more specific and should be carefully considered. A garment could have an oversized, relaxed, standard, tight, or very tight fit. An oversized garment has a finished chest measurement 6 or more inches larger than the actual chest measurement of the wearer. For a relaxed fit, the finished chest measurement is 4 to 6 inches larger. For a standard fit, the finished chest measurement is 2 to 4 inches larger, for a tight fit the finished chest measurement is 0-2 inches larger, and for a very tight fit the finished chest measurement can be the same or less than the actual chest measurement.
The designer of a garment intends a certain fit and indicates this through the combination of size and finished measurements. The actual chest measurement for a S (small) woman is 32-34 in. and for a M (medium) woman is 36-38 in. If a designer specifies size S (small) and the finished chest measurement is 40 in., because the finished measurement is 6 in. or more larger than the actual chest measurement, the intended fit is oversized. On the other hand, if a designer specifies size M (medium) and the finished chest measurement is 40 in., the intended fit is standard.
Instructions for many items, especially garments, are given for multiple sizes. This means that the instructions including the stitch counts must be given for all sizes at the same time. To do this, parentheses and commas are used to group and separate the instructions for the different sizes. For example, if instructions are provided for the three sizes S (M, L) then whenever you see numbers within the written instructions such as 9 (12, 15) sts, the first number applies to the S size, the 2nd number applies to the M size, and the 3rd number applies to the L size. Many people find it useful to circle or highlight all the numbers for the size they are making, or if a digital version of the instructions is available the numbers for all other sizes except the size being made can be deleted.
Finished measurements or a garment are the measurements of the piece itself, NOT the measurement of your body.
You may want a fit that differs from the intended fit. For example, perhaps the designer’s intended fit is standard. You love the look of the garment, but would like it in a more relaxed “lounge around the house” fit. To do this, ignore the instructions for your usual size (e.g. S, M, L) and make the size that is 4 to 6 inches larger than your actual chest measurement.
Achieving the indicated finished measurement depends entirely on achieving the indicated gauge (the number of stitches and rows worked in a piece fabric of a certain size).
It can be surprisingly difficult to visualize a specific measurement. Get out a ruler, yard stick, or tape measure and look at the finished measurements to ensure that the teddy bear you plan to knit isn’t so large it will completely fill your baby’s crib or so small your dog could eat it in one gulp.