Speed is the rate of covering distance — the most basic relationship in motion.
Speed = Distance ÷ Time
Where
| Distance | How far you traveled |
| Time | How long it took |
Worked example
Covering 120 miles in 2 hours gives 120 ÷ 2 = 60 mph.
Vehicle road speed also depends on tire size, transmission gear, and axle ratio — change a tire diameter and the speedometer reads differently.
See the Speedometer Error calculator in the automotive calculators.