at the (very) outside
At the most. The traffic wasn't that bad, so I think I'll only be 15 minutes late at the very outside. What do you think tuition will cost at the outside?
at the (very) outside
at the very most. The car repairs will cost $300 at the very outside. I'm now on my way and I'll be there in three hours at the outside.
at the outside
see under at most.
at the outˈside
(of an amount, a number, etc.) at the most; as a maximum: I doubt if this factory makes more than 500 cars a year at the very outside.