I'm not positive but think my husband was able to feel some movement at about 23 weeks. It was pretty unusual (the baby was moving pretty close to the abdominal wall) and he hasn't been able to feel it again (yet). This baby isn't a big kicker, he just slithers around, so that has a lot to do with it. :)
It depends on whether you are thin or not. I am not thin and am 24 weeks pg, my DH cannot feel my baby move.
I agree with the other posters weight matters to see movement but I was 22 wks when you could actually see like a foot or an elbow something going across my stomach. Have fun feeling the baby. This is an experience only you can really enjoy.
Close to 20wks & by 25wks or so everyone can actually see your belly waving as your baby moves :) Enjoy