[Wolfman77]

Warp 9.9 is quite a bit faster than 9.8. I have never been able to find an exact formula, but I haven't tried since 8th grade or so. Here's the approximate breakdown of the interger warp speeds:
Warp 1 - 1 times the speed of light
2 - 10
3 - 39
4 - 102
5 - 214
6 - 392
7 - 656
8 - 1024
9 - 1516
They used an Excel spreadsheet to calculate them.