R3's gear ratios, per the owners manual (U.S. model, at least) are:
1st: 2.500(35/14)
2nd: 1.824(31/17)
3rd: 1.348(31/23)
4th: 1.087(25/23)
5th: 0.920(23/25)
6th: 0.800(24/30)
So 5th and 6th are both overdrive gears
I found the gear ratios for the YZF-R25 in an owners manual PDF on the Japanese Yamaha Motors site. Not the same, at least for Japanese YZF-R25 model. Could be different for export models?
1st: 2.666 (40/15)
2nd: 1.882 (32/17)
3rd: 1.454 (32/22)
4th: 1.200 (30/25)
5th: 1.037 (28/27)
6th: 0.920 (22/25)
http://www.yamaha-motor.co.jp/manual/mc/20151WD2.pdf
I also found the R3 manual on Japanese site and ratios are the same as for the U.S. model R3 in my manual. Japanese model is designated YZF-R3A. U.S. model is designated YZF-R3F