Choose what you want to find, fill in the other two in whatever units you like, and get the answer in every common unit. Works for driving, running, cycling, flights and physics homework alike.
hours · minutes · seconds
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Speed, distance and time are linked by one formula: speed = distance ÷ time. Rearranged, distance = speed × time and time = distance ÷ speed. Everything is converted to metres and seconds first, so you can mix units — a distance in miles with a speed in km/h, for example — and still get a correct answer.
Example: 150 km at an average 100 km/h takes 150 ÷ 100 = 1.5 hours, or 1 h 30 min. Covering 10 km in 50 minutes is an average speed of 12 km/h (7.46 mph), which is a pace of 5:00 per kilometre.
A knot is one nautical mile (1,852 m) per hour and is used at sea and in aviation. 1 mph = 1.609 km/h = 0.447 m/s.
Speed = distance ÷ time. Rearranged: distance = speed × time, and time = distance ÷ speed. A handy memory aid is the triangle with D on top and S and T underneath.
Divide the distance by your average speed. 240 miles at 60 mph is 4 hours. Remember to use your average speed including stops, not your cruising speed.
Divide km/h by 1.609 (or multiply by 0.6214). 100 km/h ≈ 62.1 mph. To go the other way, multiply mph by 1.609.
Speed is distance per unit of time (km/h); pace is time per unit of distance (minutes per km), which runners and walkers prefer. 12 km/h is the same as a pace of 5:00 per km.
Average speed. If you want the time for a real journey, use a realistic average that includes slowing down, traffic and stops.
