This is the percentage of the ball buried, and therefore will effect drag on the club facce and the ball leaving its spot, reducing its trajectory and distance.
1. 20-25% = 1/2 extra club.
2. 30-40% = 1 Full club.
3. 40-50% lies = 2 or 3 clubs.
4. 50-70% requires a punch shot, regardless of where you are.
There are two distinct issues you need to remember.
a) The club. Some of the Pro Shop wedges are better in rough then others.
b) The shot type. Some shots went have the same effect (like chips/pitches/Flops)
You have to practice practice practice the shot type and the club.
As a basic rule of thumb for all begininerrs the ONLY club you should use at less then 40% power is the putter.