Measuring stockinette

Hey folks. I’m knitting a piece in stockinette, and the directions say to knit until the piece measures 13" from cast-on edge. When y’all measure stockinette, do you uncurl the bottom edge? Or do you just measure with the curl? I’m worried that I’m stretching too much when I uncurl, but I’m also worried that I’m going to run out of yarn… :shock:

Often a pattern will specify. I’d gently uncurl the bottom, without stretching too much, and measure that way.

I uncurl it and measure up to the needle.