That is insane ballooney for a 15 on a civic. To get stock rolling diameter, you'd have a 50 series tire, or maybe 55 with a 185 section width. 65 series sidewall is huge, any way you cut it.

OK, so here's the breakdown:

205/50-15 = 23.1 diameter, 72.5 rolling circumference
185/65-15 = 24.5 diameter, 76.9 rolling circumference

So it'll be an inch and a half bigger than stock, and will roll 4.5 inches farther every rotation. It will also handle like garbage and look silly, but it's your call.