Instructions
Determine which Flash to which you refer. For example, Golden Age Flash is Jay Garrick, Silver Age Flash is Barry Allen and others include Wally West and several others from the Allen family.
Consider the Flash's environments. For example, in issueÜof Flash v2, the Flash won a race against Superman in a non-hostile environment, where the latter ran at 2,000 miles a second, or Mach 9350. However, in a cold, wet environment, the Flash is considerably slower.
Calculate the Flash's top speed in a non-hostile environment depending on who he is. For example, Golden Age Flash is officially stated to run at the speed of sound, or the speed of light with speed-force assistance. Silver Age Flash is officially stated to be able to circle the world within three minutes.