I've been looking for some info on the FTL speeds of ships in Mass Effect but I have been unable to find anything. Can anyone provide a speed and sources? If not can anyone provide the time it takes to travel between two well known (in our universe) stars?
As listed in the wiki, and repeated in each of the games at one point:
FTL drives are devices which allow ships to travel at FTL speeds through space. FTL drive cores work by exposing element zero to electric currents, creating mass effect fields. It reduces the mass of an object, such as a starship, to a point where velocities faster than the speed of light are possible. With a mass effect drive, roughly a dozen light-years can be traversed in the course of a day's cruise without bending space-time and causing time dilation.
As a simple modification of e = mc^2, if you reduce mass thru
magic technological implementation of element zero, you are able to travel at light speed or further (negative mass) with reasonable power requirements.
Obviously hand waved bs, but consistent with the titular Mass Effect used for basically everything in game.
Further more FTL speeds in game vary story wise based on engine size or ship type. That said, 12 light years is 7.05419978 × 10^13 miles. That's a little under 3 times the distance to the closest star to earth, Alpha Centauri. With a Mass Effect ship, you could make it there and back in less time than it takes to drive across the US.
In Mass Effect 3, we get this Codex entry:
The Reapers' thrusters and FTL drives appear to propel them at more than twice the speed of Citadel ships. Estimates of their location in dark space suggest they can travel nearly 30 light-years in a 24-hour period.
That works out to a strict upper bound of 15 ly/day, and a rough lower bound of 10 ly/day (any slower than that and the codex would have said "three times the speed" instead of "twice the speed"). This is nicely consistent with the other answer and may be sourced to a specific in-game Codex entry (secondary codex -> The Reapers -> Reaper Capabilities). It also tells us about the reapers (30 ly/day), which the other answer does not.
Finally, it should be noted that these are daily cruising speeds, not long-term averages. Since ships in Mass Effect need to periodically discharge their cores, they cannot actually sustain these speeds indefinitely without stopping (except for the reapers, which the same codex entry says are apparently not subject to this limitation). While I'm not aware of any canonical discussion of the matter, it seems like it would be difficult to reliably find rogue planets with magnetospheres in interstellar space.
After playing Mass Effect Andromeda, where the backstory is about traveling to the Andromeda constellation in about 600 years:
I was also pondering this and wanted to put the speed of traversing 2 million lightyears in 600 years. Please do correct me when I am making a mistake in my thinking process. A web tool helped me converting 2 million lightyears to kilometers
To put it to a format that is actually readible, we'll need to go to km/s
18921460945161600000 km/600 years/365 days/24 hours/3600 seconds = 999992651km/s /c makes 3333 times the speed of light.