Speed, Distance and Time Calculator
Speed, distance and time are linked by one simple relationship, so if you know two you can find the third. Use it for planning a road trip, working out a running pace or checking a physics problem. This calculator handles kilometres, miles and metres with hours, minutes or seconds, and converts speeds to km/h, mph and m/s.
How to use the speed, distance and time calculator
- Choose what you want to find.
- Enter the two known values. The labels change meaning with your choice: for speed enter distance then time; for distance enter speed then time; for time enter distance then speed.
- Pick the units and read the answer and its conversions.
Formula
speed = distance ÷ time, distance = speed × time and time = distance ÷ speed. To convert: 1 m/s = 3.6 km/h and 1 mph = 1.609344 km/h.
Worked examples
Finding speed
150 km in 2 hours is 75 km/h, which is about 46.6 mph.
Finding distance
Driving at 60 mph for 2.5 hours covers 150 miles.
Finding time
100 km at 8 km/h takes 12.5 hours, or 12 hours 30 minutes.
Speed, distance and time in real life
Typical speeds
| Activity | km/h | mph |
|---|---|---|
| Walking | 5 | 3.1 |
| Cycling | 20 | 12.4 |
| City driving | 50 | 31 |
| Motorway | 110 | 68 |
| Passenger jet | 900 | 560 |
Running pace
A 5-minute-per-kilometre pace is 12 km/h, which means a 10 km run takes 50 minutes. Enter 10 km at 12 km/h in “time” mode to confirm.
Average speed pitfalls
If you drive half the distance at 60 km/h and half at 40 km/h, your average is 48 km/h, not 50. What matters is total distance over total time. Traffic lights and stops lower real averages, so leave a margin when planning a trip.
Unit conversions worth memorising
36 km/h is 10 m/s. 100 km/h is about 62 mph. A knot is 1.852 km/h. The unit converter handles all of these.
Practice problems
Try these yourself first, then check your answer. The answers come from the calculator above.
- A train travels 420 km in 3.5 hours. What is its speed?
Show answer
Speed: 120 km/h
- How long does a 90-mile trip take at 45 mph?
Show answer
Time: 2 h
Common mistakes to avoid
- Mixing units, such as kilometres with minutes, without converting.
- Averaging two speeds over equal distances with the arithmetic mean. Use the harmonic mean instead.
- Forgetting that stops and traffic make average speed lower than the speed you drive.
Frequently asked questions
What is the formula for speed?
Speed equals distance divided by time.
How do I convert km/h to mph?
Divide by 1.609. So 100 km/h is about 62.1 mph.
How do I find average speed for a round trip?
Divide total distance by total time. Do not simply average the two speeds.
Can I use decimals for time?
Yes. 2.5 hours is 2 hours 30 minutes.
Reviewed September 26, 2026 by the SolveCalcPro editorial team. Found a mistake? Tell us; see our editorial policy.