I want to wire a shed that is 225 ft from power I want 40 amps of service what size wire do I need for 220 volt?

I'd use #4 and a 50 or 60A breaker, not 40A.
You need to upsize the wire for that distance. This is NOT a code requirement, it is a code recommendation.


Using #6 you can pull up to 40A breaker up to around 180'.
If you jump to #4 you can pull almost 60A at 225'. Even at a full 60A the VD is NOT severe enough to even worry about.
So use the #4, but don't limit yourself at the same time. Take advantage of the larger wire.

What will you be using out there?