Speed Calculator — average speed from distance and time

How it works

Average speed answers "how fast, on average?" over a whole trip. It is the total distance travelled divided by the total time taken:

speed = distance ÷ time

This calculator is unit-agnostic — it treats distance and time as plain numbers, so the unit of the answer is whatever units you put in. Enter kilometres and hours and the speed is in km/h; enter metres and seconds and it is in m/s. The one rule is consistency: pick a distance unit and a time unit and use them for every field.

Average speed is not the same as velocity. Speed uses the actual distance travelled, so it is never negative; velocity uses displacement (straight-line change in position) and has a direction. Drive to a shop and back and your average speed is positive, but your average velocity is zero because you end where you started.

Worked example

A car covers a distance of 300 in a time of 5: its average speed is 300 ÷ 5 = 60. The presets show the pattern at other scales — 6 in 0.5 → 12 (the OpenStax store-trip example), 120 in 1.5 → 80, and 100 in 10 → 10. Halve the time for the same distance and the speed doubles; double the time and it halves.

Frequently asked questions

What is the formula for average speed?

Average speed equals total distance divided by total time: v = d ÷ t. It is the single steady speed that would cover the same distance in the same time as your actual, possibly varying, journey.

What units does this calculator use?

Whatever units you enter, as long as they match. Distance in kilometres with time in hours gives km/h; metres with seconds gives m/s; miles with hours gives mph. The calculator does not convert units for you, so keep one distance unit and one time unit throughout.

What is the difference between speed and velocity?

Speed is how fast you move; velocity is how fast **and in which direction**. Speed uses distance travelled and is always zero or positive. Velocity uses displacement — the straight-line distance and direction from start to finish — so a round trip has a positive average speed but zero average velocity.

How do I find average speed over several legs of a trip?

Add up all the distances and all the times, then divide the totals: average speed = total distance ÷ total time. Do **not** average the individual leg speeds — that gives the wrong answer unless each leg took the same amount of time.

Why does the speed disappear when I set time to zero?

Speed is distance divided by time, and dividing by zero is undefined — no time has elapsed, so there is no average speed to report. The calculator shows a blank result until you enter a positive elapsed time.

Is this instantaneous speed or average speed?

It is average speed — the overall rate for the whole distance and time you enter. Instantaneous speed (what a speedometer reads at one moment) needs calculus or a very short time interval; the average is what you get from a total distance and a total time.