General
Speed Calculator
Works speed, where the units have to be consistent before dividing.
Result
This is average speed across the whole journey, including any time spent stopped. Actual travelling speed will be higher if the time includes stops.
Get a Free Business AuditHow the calculation works
Distance divided by time. The result's units follow the inputs, which means miles divided by minutes gives miles per minute rather than miles per hour, and the conversion has to be applied deliberately rather than assumed.
What moves the number
- Units of distance and time.
- Whether the figure wanted is average or instantaneous.
- Whether stopped time is included.
- Elapsed against moving time.
Where this one goes wrong
Average speed over a journey including stops is lower than the speed while moving, and both are correct answers to different questions, which matters for anything involving a schedule rather than a performance figure. State which is meant. Averaging speeds is also not the same as averaging over distance: travelling one mile at twenty and one at sixty gives an average speed of thirty, not forty, because more time was spent at the slower speed.
Before you quote
- Make the distance and time units consistent before dividing.
- State whether stopped time is included.
- Average over time rather than averaging the speeds.
Questions
About this calculator
What is the average of travelling 20 then 60 mph?
Over equal distances it is 30 mph, not 40, because more time was spent at the slower speed. Averaging the speeds rather than averaging over time is a common error and it always overstates the result.
Should stopped time count?
It depends on the question. Average speed including stops answers a scheduling question; speed while moving answers a performance one. Both are correct and they can differ considerably on a journey with traffic.
Why do my units come out wrong?
Because the result's units follow the inputs. Miles divided by minutes gives miles per minute, and multiplying by sixty is needed for miles per hour. The conversion has to be applied deliberately rather than assumed.
The formula
speed = distance ÷ time
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How to use this calculator
- Distance. Enter your own figure; the page starts at 120.
- Distance unit. Enter your own figure; the page starts at Miles.
- Time: hours. Enter your own figure; the page starts at 2.
- Time: minutes. Enter your own figure; the page starts at 15.
The result updates as you type, so you can try a figure, see what it does to average speed, and change it back. Nothing you enter is sent anywhere or saved.
A worked example
These are the figures the calculator opens with. Every number in the results column below is produced by the same calculation the page runs, so you can follow it through before putting your own figures in.
What goes in
| Input | Value |
|---|---|
| Distance | 120 |
| Distance unit | Miles |
| Time: hours | 2 |
| Time: minutes | 15 |
What comes out
| Result | Value |
|---|---|
| Average speed main result | 53.3333 |
| In the other unit | 85.8317 |
| Distance per minute | 0.888889 |
| Time in decimal hours | 2.25 |
Covering 120 miles in 2.25 hours is an average of 53.3333 mph (85.8317 km/h).
How sensitive the answer is
Holding everything else steady and changing only distance, this is what happens to average speed. It is worth knowing which of your inputs the answer actually hinges on, and which barely move it.
| Distance | Average speed |
|---|---|
| 60 | 26.6667 |
| 90 | 40 |
| 120 example above | 53.3333 |
| 180 | 80 |
| 240 | 106.6667 |
Every other input is held at the example value while this one changes, which is not how a real job behaves. Treat it as a guide to which number matters most, not as five separate quotes.
What each figure means
- Distance
- A number, starting at 120.
- Distance unit
- Choose from Miles, Kilometres.
- Time: hours
- A number, between 0 and 10000, starting at 2.
- Time: minutes
- A number, between 0 and 59, starting at 15.
What the results tell you
| Result | What it is |
|---|---|
| Average speed | The headline result. A number. |
| In the other unit | A number. |
| Distance per minute | A number. |
| Time in decimal hours | A number. |
Keep going
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