Remember: The Google knows all.
For reference, if you want to calculate the ABV, open google.com and enter the following:
(OG - FG) * 131
Hit enter and google will tell you the ABV. For the numbers you gave, I entered:
(1.054 - 1.012) * 131 and got back:
(1.05400 - 1.01200) * 131 = 5.50200
As an aside, there seem to be around 42 different formulas for ABV, and they all come out within a few 1/10ths of a percent of each other. This is probably why what I posted differs from rsmith179's answer by 0.1%.