So VG generally had some easy to grasp unit measurements. However after looking at the stats of 20 or so League of Legends Champions I still find it hard to understand how their units are calculated. Something like attack range or radius is a bit hard to understand
So, this isn’t easy to answer precisely, because AFAIK Riot has never defined exactly what one “unit” represents. However, units for movement = units for range, so that’s consistent. Teemo has been determined to be about 100 units wide, so a while back, someone on Reddit calculated a unit as being ~0.8 cm.
To get an idea of how that translates to the map, you can look at the spell range rings. Some examples of spell ranges: