The speed-distance-time formula
Speed is defined as the distance travelled divided by the time taken. Rearranging gives distance equals speed multiplied by time, and time equals distance divided by speed. These three forms cover every combination: if you know how fast something travels and for how long, you can find how far it went; if you know the distance and speed, you can find the time needed.
Average speed differs from instantaneous speed. A journey may average 70 mph or about 113 km/h including stops and slower sections, even if the vehicle briefly travels much faster. Average speed is total distance divided by total elapsed time, and that is the quantity this online speed calculator works with.
Speed = Distance / Time
Average speed equals total distance divided by total elapsed time.
Distance = Speed x Time
Distance covered equals speed multiplied by the time spent travelling.
Time = Distance / Speed
Time required equals total distance divided by average speed.