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Speed, Distance and Time Calculator
Pick the quantity you want to find, enter the other two, and get the answer in several units at once. It handles kilometres, miles, nautical miles, knots and metres per second, and shows running pace for the speed.
The one relationship behind all three answers
Speed, distance and time are linked by a single equation, and each answer is a rearrangement of it:
distance = speed × time
speed = distance ÷ time
time = distance ÷ speed
The equation holds only when the units agree. A speed in kilometres per hour must be multiplied by a time in hours, not minutes. The calculator avoids this trap by converting every input to metres and seconds internally, computing there, and converting back to whichever units you chose.
For the marathon example, 42,195 m divided by 12,600 s is 3.349 m/s, which equals 12.06 km/h, or a pace of about 4 minutes 59 seconds per kilometre.
Units and conversions used
| Unit | Exact value |
|---|---|
| 1 mile | 1,609.344 m |
| 1 nautical mile | 1,852 m |
| 1 knot | 1 nautical mile per hour (0.5144 m/s) |
| 1 km/h | 0.2778 m/s |
| 1 mph | 0.44704 m/s |
These are the internationally agreed definitions, so no rounding creeps into the conversions. Knots are used in aviation and at sea, miles per hour on roads in a few countries, and kilometres per hour in most of the world. Pace, the time to cover one kilometre or one mile, is the reciprocal of speed and is mainly used by runners and cyclists.
Average speed is not the average of speeds
A classic mistake is averaging two speeds. If you drive 60 km out at 30 km/h and 60 km back at 60 km/h, the average speed is not 45 km/h. The outward leg takes 2 hours and the return takes 1 hour, so 120 km takes 3 hours, giving 40 km/h. Always divide the total distance by the total time.
The same idea applies to stops. Time spent at traffic lights, rest breaks or boarding gates counts in the elapsed time, so the average speed of a whole journey is lower than the speed shown on the dashboard while moving. For journeys with several legs, add all distances and all times first, then run the calculator once.
Limits
The formulas describe constant speed in a straight line. Acceleration, wind, current, hills and traffic make real trips differ, so treat results as estimates for planning. Flight and sailing times depend on ground speed rather than airspeed or speed through water. Runners should note that GPS watches smooth speed over short windows, so the average over a full run is a more dependable figure than any single reading. When planning a long drive, build in time for fuel, meals and rest, and compare the total elapsed time with the moving time, since the gap between them is often larger than expected. For a fuel estimate on the same trip, see the fuel cost calculator.
Worked example
A runner covers a marathon distance of 42.195 km in 3 hours 30 minutes. What was the average speed and pace?
Inputs
| Solve for | Speed |
|---|---|
| Distance | 42.195 |
| Distance unit | Kilometres |
| Speed unit | km/h |
| Hours | 3 |
| Minutes | 30 |
| Seconds | 0 |
Result
Distance divided by time.
| Speed | 12.06 km/h = 7.49 mph = 3.35 m/s = 6.51 knots |
|---|---|
| Distance | 42.195 km = 26.219 miles = 22.783 nautical miles |
| Time (h:mm:ss) | 3:30:00 |
| Time (decimal hours) | 3.5000 |
| Pace per kilometre | 4:59 min |
| Pace per mile | 8:01 min |
- This assumes a constant speed. For a real journey with stops, use the average speed over the whole elapsed time.
Accuracy note: Results are calculated in your browser from the values you enter. Check anything that matters for legal, academic or financial purposes against the official source.
Frequently asked questions
How do I calculate speed from distance and time?
Divide the distance by the time taken. For example, 150 km in 1.5 hours is 100 km/h. Make sure the time is in the same unit as the speed you want.
How do I find the time a journey will take?
Divide the distance by the speed. A 100 km trip at 80 km/h takes 1.25 hours, which is 1 hour and 15 minutes. The calculator shows the result as hours, minutes and seconds.
What is the difference between knots and mph?
A knot is one nautical mile per hour, and a nautical mile is 1,852 metres. A mile used on roads is 1,609.344 metres, so a knot is about 1.15 mph.
Why is my average speed lower than my driving speed?
Elapsed time includes stops, queues and slow sections, while the speed on the dashboard shows only the moment. Average speed is total distance divided by total elapsed time.
How do I turn speed into running pace?
Divide 60 by the speed in km/h to get minutes per kilometre. At 12 km/h the pace is 5 minutes per kilometre. The calculator shows both per kilometre and per mile pace.