What this calculator does
Speed, distance and time are one relationship with three faces: any one of them follows from the other two. This calculator takes a distance and the time it took and returns the average speed, which is the figure that actually determines arrival times.
Average speed is almost always lower than the speed shown on the speedometer, because it includes every moment spent stopped, slowing or turning. That gap is why a journey planned at the speed limit invariably takes longer than expected.
The formula
Divide the distance by the time, with hours and minutes combined into a single figure in hours. The other rows convert that speed into metres per second and miles per hour, and apply it to a standard 100 km distance for comparison.
| Term | Meaning |
|---|---|
| Average speed | Total distance divided by total time, including time spent stationary. |
| Instantaneous speed | The speed at one moment, which is what a speedometer shows and what a speed limit governs. |
The inputs explained
| Field | What to enter |
|---|---|
| Distance (km) | The distance covered, in kilometres. |
| Time: hours | The whole hours the journey took. |
| Time: minutes | Any additional minutes beyond the whole hours. |
When to use it
Working out a realistic travel time
Taking the average speed from a journey you have already made is a far better basis for planning the next one than using the speed limit.
Checking a pace
For running, cycling or rowing, the average speed over a known distance is the basic measure of the effort.
Comparing routes
A longer route at a higher average speed frequently beats a shorter one through traffic, and this puts numbers on the comparison.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What average speed results from covering 250 km in different times?
The same distance covered over a range of times.
| Time taken | Average speed | In mph |
|---|---|---|
| 2 hours | 125.00 km/h | 77.67 |
| 2.5 hours | 100.00 km/h | 62.14 |
| 3 hours | 83.33 km/h | 51.78 |
| 3.5 hours | 71.43 km/h | 44.38 |
| 4 hours | 62.50 km/h | 38.84 |
Questions
Why is my average speed so much lower than the limit?
Because average speed counts every second of the journey, including traffic lights, junctions and stops. On an urban trip the time spent not moving often dominates, which is why average speeds well below the limit are normal.
Can I average two speeds to get the overall average?
Not by taking the plain mean. Travelling half a journey at 40 and half at 80 does not average 60, because more time is spent at the slower speed. The correct method is always total distance divided by total time.
How much time does a faster average actually save?
Less than most people expect, and the saving shrinks the faster you are already going. Time is distance divided by speed, so equal increases in speed produce ever smaller reductions in time.
What does the 100 km figure mean?
It applies the calculated average speed to a standard 100 kilometre distance, which makes two different journeys directly comparable regardless of how long each one actually was.
For converting the result between units, see the speed unit converter. For working an average out across several legs, see the average speed calculator.