Formula:
Speed (m/s) = (π × Diameter in meters) × (RPM ÷ 60)
Speed (mph) = Speed (m/s) × 2.23694
Formula:
RPM = (Speed in m/s ÷ (π × Diameter in meters)) × 60
or
RPM = ((Speed in mph ÷ 2.23694) ÷ (π × Diameter in meters)) × 60