Depends on what the pattern says if I use one. I'm doing a Kimberbell quilt and it's only 32" square. A little small for me so I'm adding an inch to the borders. If i'm picking the size I keep the square within WOF so 40ish so I don't have to piece the back
. Also depends on who is getting it. I make a bunch for my coworkers on a large nursing unit. Those tend to be on the smaller side around 36 square. If it's a relative, good friend or someone special - I tend to go rectangle and a little bigger. I'd say 46 is plenty long enough you might want to add a row to the width. Honestly, they're going to love and the size doesn't matter.