Ι will try to Answer your question!

Zoom - Last known speed : Mach 13.6

Savitar - Last known speed : in speed force = Mach 57 - Out of it : Mach 16

Trajectory - Last known speed : Mach 5

Flash : Mach 1776000 or 2c. or twice the speed of light…. Wow… and he in season 5 he created more than 2.5 Billion Joules!! THAT'S CRAZY. And as well in a secret scene that Grant Released for a little time that flash reversed time.

Kid Flash - Flashpoint : Mach 9 = Normal World : Mach 45

XS : Mach 46

Iris Speedster : Mach 2.3

Jesse Quick : Mach 37

Reverse Flash : Mach 8

Flash Earth 3 : Mach 12

Accelerated Man : Mach 6

Flash Earth 90 : Mach 34

Flash Earth 90 isn't Flash Earth 3 bt they are played by the same actors!

Hope that'll answer your question buddy! Officially Barry is the fastest speedster! And remember Mach 880,000 is the speed of light and these speeds are calculated.

They are all their max speeds! Not their usual

The Flash's speed normally is a little below Mach 440,000 But he has to slow himself down for Nora….

THIS IS ONLY RELATED TO SEASON 5

And as well… Mach is the speed of sound so byeeeee

Edit : Almost 500 hundred views :D Thanks!!!

I added A few facts and Updated their speed