Hi!, why is everybody talking about Tables?? Come on people! even my simulator program is fast enought to calculate it real time!.
Constants:
T Time between pulses in Seconds
D Wheel round/size in meters (pi*diameter) or (pi*(radius*2))
S Speed
Formula:
S:=(1/T)*D
(s now is in meters a second!
S:=S*3.6
(now its Kilometers a hour)
S:=S/1.6;
(Now its Miles an hour)

Little check:
wheel = 0.5*pi = 1.5meters
200/3.6 = 55 Meters a Second
55/1.5 = 35 Pulses a second
1/35 = 0.02 Seconds between pulses


Lets say we measure 0.04 seconds between pulses
d = 0.5*pi = about 1.5 meters

1/0.04=25 Pulses a second
25*1.5=37.5 Meters a Second
37.5*3.6=135 Kilometers an Hour

so 25 pulses a second.
25/8=3.1
3.1 times a second updating the value on a character based LCD is enough (more would make it all blurry)

Why div my 8? Id recommend to use 3 Flipflops (2*2*2=8) before the input, so when 8 pulses has come to the wheel one only gets to the micro, this gives more time to calculate and with bigger numbers.

I really don't see why you guys are talking about a Table???????????

Anybody got suggestions or comments or sees errors/unrealism in this please respond!