Measure it, and then look up what it is normal for your model.
You'd have to run that one by someone at Tire Rack or Discount Tire as they have the specs. I assumed you were looking at recommended size, not going outside the norm, which is something I do not experiment with.
The offset of a rim has to do with measuring your rim, not the tire that would fit that rim.
I worked with Fitment industries, lots of options and knowledgeable staff plus you can view examples that will show you how the offset will look. They also have calculators so you can mess with different combinations
If you have stock suspension, I would use 225/45R18. That's what I have on 18x8 +55 and stock suspension. They're only 1% larger than stock, and follows the natural progression of "plus sizing" (205/60R16, 215/50R17, 225/45R18, etc.).