Number of stitches to knit a cuff

I want to add a knitted cuff onto a coat sweater. I am using size 7 US dpn and my wrist is 7 1/2 inches, how many sts should i cast on to join in round?

It depends on the yarn you’re using and the gauge you get in pattern stitch. You could try a swatch in whatever pattern stitch you want to use (k1p1 or k2p2 rib or whatever). Then you’ll know how many sts to cast on.

I’m using a double strand. I think I’ll try k2p2 and test for measurement along the way. Thank you.