Question about percentages in baseball

#1
Ok, I have a basic understanding of statistics but need help to figure out this one. If you know about baseball then it'll be easier for you to understand:

Jason Kubel had 13 home runs last year, and if he gets the same amount of at-bats that he did last year, this year, he's on pace for 20 home runs. What I'm trying to figure out is, how much of a percentage increase is that and how do you figure it out?
What I want to say is "On the other hand, he's on pace to increase his HR production by __%" [13 in the previous year followed by 20 in the next].

Does that make sense?
 

Mean Joe

TS Contributor
#2
What I'm trying to figure out is, how much of a percentage increase is that and how do you figure it out?
Kubel is on pace to increase his homeruns by 7. To express as a percentage, you divide by the original amount.

So % increase = increase / original = 7/13 = .538 or 53.8%