In reply to luke glaister: It sounds like what you really want to know is "how do I break into a new grade outside?" rather than "What trad grade could I climb with my current strength if my head was wired like Alex Honnold?"
In which case, I'd say it is often hard to break into a new grade but breaking it down into a few mini steps might help, e.g:
1) get some topropes on some harder routes, you don't need anyone to climb the route, just go round to the top of the crag and set up a toprope on the desired climb.
2) try leading a climb of the next grade after a few goes on it toprope.
3) try leading a climb of the next grade after just abseiling down it, having a pull on the holds and a look for the gear.
4) try onsighting a climb of the next grade.
5) consolidate the next grade by forcing yourself to get on something that hard on as many of your outdoor trips as you can (I often find that if I break into a new grade I celebrate and then quietly back back down to the previous grade and suddenly the conviction needed to climb your new grade is like you have never done it all over again!).
All off the above are suggestions if you don't have a partner who climbs harder than you.