4 tools
Translate road speeds and motion between kilometres, miles and metres per second.
Choose a conversion below. Every tool includes an instant result, an example and a short explanation.
Speed combines distance and elapsed time. A mile is exactly 1.609344 km, so one mph equals 1.609344 km/h. One metre per second equals 3.6 km/h because an hour has 3,600 seconds and a kilometre has 1,000 metres.
These units appear in road signs, weather reports and physics. Check whether the source gives instantaneous speed, average speed or a limit: conversion does not make those concepts equivalent. For travel estimates, time stopped in traffic changes the average even when the speedometer briefly shows the converted value.
No. A speed conversion changes units for the same rate, such as miles per hour to kilometres per hour. Travel time also needs a distance and an assumption about the speed along the route. A posted limit, a vehicle’s instant reading and a journey average are different quantities even when all use km/h.
A kilometre contains 1,000 metres and an hour contains 3,600 seconds. In one hour, a constant speed of one metre per second covers 3,600 metres, or 3.6 kilometres. This exact relationship is useful when moving between weather, road and laboratory speed reports.