Speed Calculator

Speed, distance and time are tied together by one equation: speed = distance ÷ time. Rearranged, distance = speed × time and time = distance ÷ speed. Enter any two values and the calculator finds the third, in whichever units you choose: kilometres or miles per hour, metres per second, or knots for water and air. Units are converted automatically, so you can enter a distance in kilometres and a time in minutes and read the answer in mph.

A knot is one nautical mile (1,852 m) per hour; the nautical mile is one minute of latitude, which is why ships and aircraft still use it. Sound travels at about 343 m/s (1,235 km/h) in air at room temperature; light at 299,792 km/s.

• Road trip. 450 km at an average of 90 km/h (allowing for stops) takes 5 hours. Enter distance and speed to get the time.
• Running. 10 km in 50 minutes is 12 km/h, or 5:00 per kilometre. For pace (minutes per km or mile) and race predictions, the pace calculator is the specialised tool.
• Cycling. 40 km in 1 h 36 min is 25 km/h.
• Physics homework. A car covers 120 m in 6 s: 20 m/s, or 72 km/h. The tool shows the intermediate conversion.
• Flights. 5,500 km at 850 km/h is about 6 h 30 min, before taxiing and headwinds.

To measure the time yourself, the stopwatch and lap timer give you the input; to convert the result into other time units, the time unit converter.