Socks for fiance

I’m starting the socks my fiance wants. The ball of his foot is 10 inches all the way round.Im doing toe up socks.
How many stitches should I increase to for it to fit his foot?

Is it a surprise? The easiest way to check will just be to have him try them on as you get going…super easy with toe ups. If you’re using a sock weight yarn you’ll probably end up increasing to somewhere between 60-80 sts depending on your gauge.