Speed Distance Time Calculator
Solve for speed, distance, or time using the fundamental relationship: Distance = Speed × Time.
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How to use this calculator
Set the unknown to 0 and the calculator solves for it using D = S × T.
- 1
Enter two known values (distance, speed, or time).
- 2
Set the unknown value to 0.
- 3
The calculator solves for the missing quantity.
- 4
Results are shown in both km and miles.
Frequently asked questions
How do I tell the calculator which value to solve for?
Leave exactly one of the three fields at 0 and fill in the other two. Leaving none at 0, or two or more at 0, returns an error asking for exactly one unknown. Because 0 means “unknown”, you cannot calculate with a genuine zero, such as a stationary object at speed 0.
Which units does it use?
The fields are labelled kilometres, kilometres per hour and hours. The arithmetic itself is unit-agnostic, so miles with mph or metres with m/s work too, but the displayed labels still say km and km/h, and the “In miles” line applies a km-to-mile factor of 0.621371 that would then be wrong. Enter kilometres if you want the miles line to be meaningful.
How do I enter minutes?
Convert minutes to hours by dividing by 60 before entering: 45 minutes is 0.75 hours and 90 minutes is 1.5. The result row shows the time both as decimal hours and as hours and minutes, so 3.75 hours appears as 3h 45m.
Is the answer an average speed?
Yes. Distance ÷ time gives the average speed over the whole trip. It says nothing about stops, traffic, hills or speed limits, and the instantaneous speed on the dial can be higher or lower than the average at any moment. For a journey with several legs at different speeds, add the distances and the times separately and then divide the totals.
Why does a time like 1.9999 hours show as 2h 0m?
The hours-and-minutes display rounds the total to the nearest whole minute before splitting it, so values just under a full hour roll over cleanly to the next hour instead of showing something like 1h 60m. The decimal-hours figure beside it is not rounded this way.
Can I enter negative values?
No. Negative distance, speed or time returns an error. The tool works with magnitudes only and has no notion of direction, so it cannot model velocity as a vector or a return trip.
How many decimal places are shown?
Up to four, with trailing zeros removed. Marathon distance, 42.195 km, covered in 3.5 hours returns an average speed of 12.0557 km/h, which is rounded rather than exact.
Speed, distance and time calculator — solve any one from the other two
The relationship and how to rearrange it
Distance equals speed multiplied by time. Rearranged, speed is distance divided by time and time is distance divided by speed. Leave the unknown field at 0, fill in the other two, and the calculator returns all three quantities, plus the distance and speed converted to miles and mph.
| To find | Formula | Inputs | Result |
|---|---|---|---|
| Distance | speed × time | 90 km/h, 2.5 h | 225 km |
| Time | distance ÷ speed | 300 km, 80 km/h | 3.75 h (3h 45m) |
| Speed | distance ÷ time | 42.195 km, 3.5 h | 12.0557 km/h |
Worked example: planning a drive
A 300 km drive at an average of 80 km/h takes 3.75 hours, which the calculator shows as 3h 45m. The same trip expressed in miles is 186.4113 mi at 49.7097 mph. If you can raise the average speed, the time falls in proportion, but keep in mind that the average includes stops, so a driver cruising at 80 km/h will usually average less over a full journey.
Worked example: a marathon pace
A marathon is 42.195 km. Finishing in 3.5 hours means an average speed of 12.0557 km/h, which is 7.4911 mph over 26.2187 miles according to the calculator. Runners often think in minutes per kilometre rather than km/h, so the result is a starting point for converting to the pace unit your watch uses.
Converting between common units
Keep the units consistent across all three fields. If distance is in kilometres, speed must be in kilometres per hour when time is in hours. Minutes become decimal hours by dividing by 60. The calculator’s own km-to-mile factor is 0.621371, so 225 km, the default distance, displays as 139.8085 mi at 55.9234 mph.
| Minutes | Hours to enter |
|---|---|
| 15 | 0.25 |
| 30 | 0.5 |
| 45 | 0.75 |
| 90 | 1.5 |
What the number does not account for
The result assumes a steady average speed, so acceleration, rest stops, and changes in terrain are all folded into whatever average you provide. It also works with magnitudes only; there is no direction, so displacement and round trips need to be handled by you before entering values. If a trip has several legs, run each leg separately, add the distances and the times, and then solve once more for the overall average. Averaging the leg speeds directly gives the wrong answer unless the legs took equal time.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →