Speed, distance and time calculator
Give any two of speed, distance and time to get the third. Breaks are added separately, and the arrival time is worked out from now — usually the thing you actually wanted to know.
- Total including breaks
- 4 h 25
- Arrival if you leave now
- October 21, 2026
- In km/h
- 152.89
- In mph
- 95.00
- In m/s
- 42.47
- Covered each hour
- 95 mi
The formula
v = d / t, d = v · t, t = d / v. Average speed means the whole distance divided by the whole time, which is why it is always lower than the speed shown on the dashboard.
Worked example
420 km at an average of 95 km/h takes 4 hours 25 minutes. With 30 minutes of breaks, the journey is 4 hours 55.
How to use it
- 1Use a realistic average, not the speed limit. On a long motorway drive, 100 to 110 km/h is a typical average against a 130 limit once junctions and traffic are counted.
- 2Add break time for anything over two hours, both because it is safer and because it changes the arrival time materially.
- 3Switch the unit first: distance follows whichever unit the speed is in.
Questions people ask
Why does my journey always take longer than this?
Because average speed is not cruising speed. Junctions, towns, roundabouts, fuel stops and congestion all count, and they typically cost 15% to 25% against the limit.
How do I average two legs at different speeds?
Not by averaging the speeds. Add the distances, add the times, and divide. 100 km at 100 km/h then 100 km at 50 km/h averages 66.7 km/h, not 75.
Last reviewed: 2026-10-20