how many inches is 64 rows in a k1,p1 pattern
Many, many variables here. What size needles, what type of yarn, what’s your gauge? All of these things determine how long your ribbing will be. You should do a swatch at least 4" square in the needles and yarn you’ll be using, then you can determine from the swatch.
That is going to depend on a few things. The weight of the yarn (fingering, worsted, bulky), the size of the needles and your own personal guage (how tight or loose you knit) will all affect how many inches 64 rows of K1P1 knitting will be.
Short version: It depends. :knitting:
You measure your knitting to find out how many rows to the inch. If it’s a pattern, see how many rows in the pattern’s gauge.