Why do I have to knit a swatch?
Each knitting pattern is based on a specific yarn and needle size. And with these specific materials a knitting tension is given. For example 10 cm x 10 cm is 22 stitches and 28 rows. Now, however, everyone knits differently. One person knits very loosely while another knits very tightly. The result of this is that even if you use exactly the yarn from the pattern with the indicated needle size, a sweater or other piece of work can still turn out very spacious or just very tight. It is therefore very important to always make a test piece before you start knitting, for example, a sweater.
It is important to knit a test piece if you use the yarn as described in the pattern and just as important if you use other yarn so that you can calculate the number of stitches.