majenko:
That is, of course, assuming the OP has measured the wheel in inches. If they have the size of the wheel in cm, then the values will be different. Simpler then to convert to km/h as they're the same kind of unit.RPM * circumference (in cm) = cm/m. Multiply by 60 for cm/h. Divide by 100,000 for km/h. Multiply by 1.609344 to convert km/h into mph.
Agreed. As the OP has given no location in his ID, I had assumed (maybe wrongly) he's in the US or UK. I do wish that people would give some sort of location in their ID. A country would be nice, a town or city would be even better.