Propulsion Scales (Earthfleet)
In the Earthfleet Universe, there are a number of different ways in which the various races determine the current and maximum flight speed of a vessel at both sublight and FTL. Some of this depends on the actual propulsion system being used, and some on the race that is using it. Listed below is the most common systems of speed measurement used within the galaxy, both standard and unique.
Earthfleet - AUT
In the Sol Sector, where Earthfleet operates, the primary measure of speed is the AUT or "Astronomical Units over Time". This uses the globally accepted "Astronomical Unit" as its chief form of measurement for both distance, and speed when traveling at either FTL or sublight. An Astronomical Unit is the average distance between the surface of the sun and the surface of the Earth. The distance is only considered as "average" because the Earth's distance to the sun varies depending on the time of year. An AU is measured in several ways. It's calculated as being 149,597,900 Kilometers or 92,955,810 miles, depending on your preferred method of measurement.
At light speed (about 186k miles per second) it takes roughly 8 minutes and 20 seconds to cross this distance. This measurement of speed is then broken down by increments of hours, minutes and seconds. So 100AUH is 100AU per hour, which is roughly 92,955,810 miles X 100 / 186000 = 49,976.24 light seconds, 832.94 light minutes, or 13.88 light hours. In short, a ship traveling at 100AUH would travel the same distance in an hour that it would take light 13.88 hours to cross. As another example, a ship moving at 60k AUM could cross a distance of around 20k light years in roughly 14.6 days. That's approximately 21k seconds, or 350.4 hours of total flight time. Five times that and the ship could cross the entire width of the galaxy one time.
Warp Speed - Galactic Standard Scale
Unlike with Coaxial and Hyper Drive, Warp Speeds are determined by power scales, with each step being exponentially higher than the previous one. Each step on the warp scale also corresponds to a multiplier of light speed. For example, warp 1, being the baseline metric, is equal to the speed of light. All other metrics above this are exponential in nature with Warp 15 coming in at close to 500k times the speed of light. This is roughly 0.96 light years per minute. However, not every warp powered ship can reach this speed, nor is it the theoretical speed cap. Some ships are capable of surpassing Warp 15. However, such speeds are generally considered to be "emergency velocity" and are only capable of being achieved for brief times by a small number of elite military vessels within the galaxy. In Warp speed terms, this roughly equates to having the peddle jammed into the firewall with the engine operating at maximum possible output. Anything faster and the ship risks catastrophic rupture of the warp nacelles due to plasma over-pressure. So at this point, the only thing that keeps ships from surpassing Warp 15 is the durability and ruggedness of their own warp drives, and their ability to continue operating under such high reactor and nacelle pressures.
The Grand Scale, while older, is still commonly used within the galaxy by numerous races. Speeds on the Grand Scale are denominated according to the standard galactic calendar, which is 360 days long, with each standard day being 26.5 Sol hours. Individual steps are determined on the Grand Scale using a "Light Years Per Standard Day" methodology. So, for example, if you were traveling at a speed of 15 light years per day, your speed would be rated as 15GS. In Sol time, that would be an equivalent speed of 13.59 light years per one Earth day.
There are a variety of other, lesser used scales that can be found all across the galaxy. For example, with the Razkor, as their primary FTL drive system is the Jump Drive, their "speed" is denoted in distance traveled per jump. For a handful of the races who prefer to use Wormhole Drive, Slipstream or Hyperluminal FTL drive systems, they measure speed by distance traveled, but denominate their distances in terms of sectors and parsecs crossed, rather than Light Years. So if you were counting your speed by sectors per day, and you were going 9Sec, your would cross 9 complete sectors of space in one day. To go 3.4PS means you've crossed 3.4 parsecs per day. If you go 3.4Sec, then you've crossed 3 sectors and 4 parsecs, with a galactic standard sector being 15 parsecs wide, and a parsec being 3.97 light years. As such, speed ratings of 3.14Sec (3 sectors, 4 parsecs) are possible. There are also a number of other, less commonly used scales, most of which are derived from local or regional scales of distance and time that do not directly correspond to galacticly accepted standards of measurement.