Speed, Distance and Time Calculator
Enter any two of speed, distance and time and get the third. Switch units between kilometres, miles, metres and knots, see running pace, or add up a trip made of several legs to find its true average speed.
Your result
Fill in the boxes above to see the result.
Results assume a steady speed, so for a real trip they are the average over the whole journey. Figures are rounded for display.
Three quantities, one relationship
Speed, distance and time are tied together so tightly that knowing any two gives you the third. You drive 150 kilometres in two and a half hours, and your average speed was 60 km/h. You know you will cruise at 800 km/h for a 3,200 km flight, so you can expect about four hours in the air. Most trip-planning questions boil down to one of these three.
The sums are simple, but they go wrong in a few predictable places: mixed-up units, minutes typed as if they were decimal hours, and the average speed of a trip with different legs. This calculator takes care of all three, and the guide below explains the thinking so you can check any answer yourself.
How to use this calculator
- Speed: enter the distance and the time taken. You get the speed in your chosen unit, and also in km/h, mph, m/s and knots, plus running pace when the speed is in a sensible range.
- Distance: enter a speed and a time to see how far you will go.
- Time: enter a distance and a speed to see how long it will take, with a table of times for common race distances at that speed.
- Multi-leg trip: list each leg’s distance and time to get the true average speed for the whole trip. Add a leg with a distance of 0 to include a stop.
The formulas
Speed = distance ÷ time
Distance = speed × time
Time = distance ÷ speed
Average speed of a trip = total distance ÷ total time
Units must agree. Kilometres and hours give km/h. Miles and hours give mph. Metres and seconds give m/s. If your distance is in miles and your speed is in km/h, convert one of them first. The calculator does that for you behind the scenes by working in metres and seconds and converting back at the end.
Worked examples
A drive
150 km in 2 hours 30 minutes. Two and a half hours is 2.5, and 150 ÷ 2.5 = 60, so the average speed is 60 km/h, which is about 37.3 mph.
A flight
2,400 miles at 480 mph. Time = 2,400 ÷ 480 = 5 hours.
A run
10 km in 52 minutes. Speed = 10 ÷ (52 ÷ 60) = 11.54 km/h. Pace is the other way round: 52 ÷ 10 = 5.2 minutes per kilometre, which is 5:12 per km, or about 8:22 per mile.
The average speed trap
You drive 60 km at 30 km/h through town, then 60 km at 60 km/h on the motorway. Many people say the average is 45 km/h. It is not. The first leg takes 2 hours and the second takes 1 hour, so you cover 120 km in 3 hours, which is 40 km/h. You spent twice as long at the slow speed, so it pulls the average down further than a plain mean suggests. The Multi-leg trip tab shows both figures side by side.
Speed unit conversions
The same speed looks very different depending on the unit, which is why road signs, car dashboards, weather forecasts and ship logs can seem to disagree. Here are the common values side by side.
| km/h | mph | m/s | Knots |
|---|---|---|---|
| 10 | 6.21 | 2.78 | 5.40 |
| 30 | 18.64 | 8.33 | 16.20 |
| 50 | 31.07 | 13.89 | 27.00 |
| 80 | 49.71 | 22.22 | 43.20 |
| 100 | 62.14 | 27.78 | 54.00 |
| 120 | 74.56 | 33.33 | 64.79 |
As a rule of thumb, multiply km/h by 0.62 for mph, divide km/h by 3.6 for m/s, and divide km/h by 1.85 for knots.
Pace and speed for runners
Runners often think in minutes per kilometre or per mile rather than speed. The two are reciprocals of each other, so you can switch between them with 60 ÷ pace in minutes. A 6:00 per km pace is 10 km/h, and 5:00 per km is 12 km/h.
| Pace (min/km) | Speed (km/h) | Speed (mph) |
|---|---|---|
| 7:30 | 8.00 | 4.97 |
| 6:00 | 10.00 | 6.21 |
| 5:30 | 10.91 | 6.78 |
| 5:00 | 12.00 | 7.46 |
| 4:30 | 13.33 | 8.28 |
| 4:00 | 15.00 | 9.32 |
If you enter a distance and your finishing time on the Speed tab, the calculator gives you pace per kilometre and per mile straight away. On the Time tab, the table underneath lists how long a 5 km, 10 km, half marathon or marathon would take at that speed.
Averaging a trip with several legs
The rule is to add up everything and divide once: total distance over total time. Never average the speeds themselves unless every leg took exactly the same time. Stops count as time, so if you want your door-to-door average, include breaks as a leg with a distance of 0. If you only want your moving average, leave them out.
This also explains a classic puzzle. If you go up a hill at 10 km/h and come back down the same road at 30 km/h, your average over the round trip is 15 km/h, not 20. Going up takes three times as long as coming down, so the slow part dominates.
Common mistakes
- Typing 1 hour 30 minutes as 1.30 hours. It is 1.5 hours.
- Mixing units, such as miles with km/h.
- Averaging leg speeds instead of totalling distance and time.
- Forgetting that a plane’s ground speed differs from its airspeed because of wind.
- Leaving out stops and traffic, so the planned time is too optimistic.
Frequently asked questions
What is the formula for speed, distance and time?
Speed = distance ÷ time. Rearranged, distance = speed × time and time = distance ÷ speed. If you know any two of the three, you can find the third. The only thing to watch is that the units match: kilometres with hours give km/h, and miles with hours give mph.
How do I find the average speed of a trip with different legs?
Add up all the distance, add up all the time, and divide. Do not average the individual speeds. Driving 60 km at 30 km/h and then 60 km at 60 km/h takes 2 hours + 1 hour = 3 hours for 120 km, so the average is 40 km/h, not 45. The Multi-leg trip tab does this and also shows the simple average of the leg speeds so you can see the difference.
Why is the average speed not just the mean of my speeds?
Because you spend more time at the slower speed. Speed is distance per unit of time, so each leg has to be weighted by how long it lasted. Only when every leg takes the same amount of time does the simple mean of the speeds match the true average.
How do I convert km/h to mph?
Multiply km/h by 0.6214 to get mph, or divide by 1.609. So 100 km/h is about 62.1 mph. To go the other way, multiply mph by 1.609: 60 mph is about 96.6 km/h. The calculator shows your speed in km/h, mph, m/s and knots at the same time.
What is pace and how does it relate to speed?
Pace is time per distance, the reverse of speed, and runners use it more than speed. A speed of 12 km/h means 5 minutes per kilometre, because 60 ÷ 12 = 5. The calculator shows pace per kilometre and per mile whenever the speed is in a range that a person on foot or bike could plausibly manage.
Can I enter the time in hours, minutes and seconds?
Yes. There are separate boxes for hours, minutes and seconds, and you can leave any of them empty. 1 hour 20 minutes can be typed as 1 and 20, or as 0 and 80, and you will get the same answer.
What is a knot?
A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 metres. Ships and aircraft use knots. 10 knots is about 18.5 km/h or 11.5 mph.
Does the calculator work for walking, cycling and running?
It does. Enter the distance you covered and the time it took to get your average speed and pace, or enter a target speed and a distance to see how long a route should take. The table underneath shows the time needed for common race distances at your speed.
Is the answer exact for a real journey?
It is exact for a constant speed. Real trips include traffic, stops, hills and wind, so treat the result as the average over the whole trip. For planning, many people add a margin on top of the calculated time.
What speed is 1 metre per second in km/h?
Multiply metres per second by 3.6. So 1 m/s is 3.6 km/h, 10 m/s is 36 km/h, and 27.78 m/s is 100 km/h. Divide by 3.6 to go the other way.
Is anything I enter saved or sent anywhere?
No. Everything is calculated in your browser. Nothing you type is uploaded or stored on our servers.
Related calculators
To add up durations or find the hours between two clock times, use the time calculator. For fuel use on a journey, try the fuel economy calculator, and for the number of days between two dates, the age and date calculator.