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How to use
This calculator solves the speed-distance-time relationship in any direction: provide two values and it returns the third. For average speed, the calculation is total distance divided by the total elapsed time you choose to include, with km/h, mph and m/s shown together.
- Choose whether to solve for speed, distance or time.
- Enter the two known values and select their units.
- For a time input, use hours, minutes and seconds; minutes and seconds must stay below 60.
- Review the result and equivalent units to check that the inputs were consistent.
How it is calculated
Example
Example: 150 km in 2 hours gives an average speed of 75 km/h, about 46.603 mph or 20.833 m/s. In reverse, 75 km/h for 2 hours gives 150 km.
Important notes
Do not confuse average speed with the simple arithmetic mean of segment speeds. The correct trip average is total distance divided by total time. Include stops in the time if you want stop-inclusive trip average; exclude them if you want moving-time average.
Worked examples and interpreting results
Traveling 60 km at 60 km/h and another 60 km at 30 km/h takes three hours. The trip’s average speed is 40 km/h because total distance is divided by total time.
| Case | Calculation | Result |
|---|---|---|
| Time for both legs | 60/60 + 60/30 | 3 h |
| Average speed | (60 + 60) ÷ 3 | 40 km/h |
How to check the result
A simple mean of 60 and 30 gives 45, which does not describe this trip because the travel times differ. Decide whether stops count toward total time; that choice changes the trip average.
Frequently asked questions
Is average speed just the average of two speeds?
Not generally. Use total distance ÷ total time; a simple mean is valid only in special equal-time cases.
Should stops be included in time?
Include them for a whole-trip average; exclude them if you specifically want a moving-time average.
Is this the same as a speed converter?
No. A converter changes units of a known speed; this calculator solves speed, distance or time from the other two.