Is a gauge swatch included in the yarn requirements?

Have you ever wondered if designers factor in a little extra yarn to account for your gauge swatch? The short answer is yes... and no. The consensus amongst my designer friends is we generally add about 10% to the yarn requirements for our patterns so you don't run out of yarn before you finish knitting your project.

Designers know that slight differences in gauge and irregularities in the actual length/mass of your skein (compared to the label) are just a natural part of knitting. To account for that, we factor in a little extra yarn. Most of the time if you are knitting a multi-skein project, like a sweater, the 10% buffer is likely going to be enough to knit one, or maybe even two gauge swatches in addition to your project.
But what about single skein projects? Designers still add about 10% to the yarn requirements for small projects but it may not be enough to also knit a swatch. If your gauge doesn't match on the first try and you need to change your needles and knit swatch number two I can almost guarantee you won't have enough yarn left for your project.
Think of it this way. If you plan to knit a hat with bulky yarn and the pattern recommends using a 132 yd/100g ball of yarn, the designer has likely factored in at least 10% extra, so you'll probably use less than 119 yds of yarn. However it's just not realistic that anyone can knit an appropriately sized swatch (in the round because a hat is knit in the round) with just over 13 yds of bulky yarn.
Play it safe and get an extra skein for swatching.
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