

In Voyager and TNG it has been established that warp 10 is infinite velocity, that means the warp scale is not linear (the differencr between warp 9 and 8 must be higher than the difference between 8 and 7). After all, Voyager’s max speed of 9.975 is faster than Enterprise D’s 9.6.
Then again, warp speed has always been quite inconsistent, so who knows which scale they are using…
Didn’t know about that formula. Is it used behind the scene but never mentioned, or just used retroactively to explain the difference between the different series?