Speed, distance and time calculator
Find speed, distance or time from the other two, or work out the average speed over two legs of a journey. Use matching units (kilometres with km/h, or miles with mph). The working is shown.
Worked example
With the values shown above when the page opens:
Time: 2 hours 30 minutes
- Time = distance ÷ speed
- = 150 ÷ 60
- = 2.5 hours = 2 hours 30 minutes
How it works
- The three are linked by distance = speed × time, so speed = distance ÷ time and time = distance ÷ speed.
- Keep the units matching: kilometres with km/h and hours, or miles with mph and hours. Convert minutes to hours by dividing by 60.
- For a journey in two parts, average speed is total distance ÷ total time, not the average of the two speeds.
Questions
Why is the average speed of a round trip lower than the average of the two speeds?
You spend longer travelling at the slower speed. Going at 40 and returning at 60 gives an average of 48, not 50.
How do I convert km/h to m/s?
Divide by 3.6. So 72 km/h is 20 m/s. To go the other way, multiply by 3.6.
How do I find the time when two people travel towards each other?
Add their speeds and divide the distance between them by that. Two cars 300 km apart at 60 and 90 km/h meet after 2 hours.
Related
Calculators are for learning and quick checks. Check important figures yourself, and do not rely on them for tax, legal or financial decisions.