Dpends on many things inc thickness of yarn and most importantly your gauge. A rough guide fior me is a row of knitting is 3 times the length of the row. Is there any particular reason why you want to know? If you fear running out of yarn starting with using up scraps with striped garter squares is surprisingly thrifty. I mostly make granny squares and know with 100g dk balls I can get 5 squares out of each ball.
Hi Mary! Thank you. I'm looking into ordering yarn and didn't want a lot of squares of one color especially. Not so much that the kids would mind, I just like to mix it up. I use slightly chunky yarn and use the size 10 needles. Some come in 80yd skeins and some 197 yds so there can be a big difference. Just kind of curious too.