The speed, distance and time formula
Speed, distance and time are linked by one simple formula: speed is distance divided by time. If you know any two of them, you can work out the third. The formula triangle is an easy way to remember all three versions: cover the value you want, and the other two show you what to do.
The units have to match. Miles and hours give miles per hour (mph), kilometers and hours give kilometers per hour (km/h). Minutes need converting first: 2 hours 30 minutes is 2.5 hours, not 2.30. This calculator takes care of that when you type the time as 2:30.
Examples
- Driving: you drive 150 miles in 2 hours 30 minutes. Your average speed is 150 ÷ 2.5 = 60 mph, or 96.56 km/h.
- Travel time: a 240 km trip at an average of 80 km/h takes 240 ÷ 80 = 3 hours.
- Cycling: riding for 1 hour 15 minutes at 20 km/h covers 20 × 1.25 = 25 km.
- Walking: at 3 mph, a 4.5-mile walk takes 4.5 ÷ 3 = 1.5 hours, or 1:30.
Average speed with stops
Average speed is always total distance divided by total time. On a long drive, breaks for fuel, food or traffic count as part of the time, so your average ends up well below your cruising speed. Driving 300 miles at a steady 60 mph takes 5 hours. Add 45 minutes of stops and the average for the whole trip falls to 300 ÷ 5.75 = 52.17 mph.
A common trap is averaging two speeds. If you drive 60 miles at 30 mph and 60 miles back at 60 mph, the average is not 45 mph. The trip takes 2 hours plus 1 hour, so it is 120 miles ÷ 3 hours = 40 mph. You spend more time at the slower speed, so it counts more.
Travel time for 100 miles or 100 kilometers
| Typical for | mph | 100 miles | km/h | 100 km |
|---|---|---|---|---|
| Walking | 3 | 33:20:00 | 5 | 20:00:00 |
| Running | 6 | 16:40:00 | 10 | 10:00:00 |
| Cycling | 12 | 8:20:00 | 20 | 5:00:00 |
| Fast cycling | 20 | 5:00:00 | 30 | 3:20:00 |
| City driving | 30 | 3:20:00 | 50 | 2:00:00 |
| Main road | 45 | 2:13:20 | 80 | 1:15:00 |
| Highway | 60 | 1:40:00 | 100 | 1:00:00 |
| Fast highway | 75 | 1:20:00 | 120 | 0:50:00 |
Times are in hours, minutes and seconds at a steady speed, with no stops. Real trips take longer because of traffic, lights, hills and breaks.
How to use the speed distance time calculator
- 1Choose miles and mph or kilometers and km/h, then pick what you want to find: speed, distance or time.
- 2Enter the two values you know. Type the time as h:mm or h:mm:ss, like 2:30.
- 3Read the result with conversions to mph, km/h, meters per second and knots, and check the table for travel times at common speeds.
Frequently asked questions
What is the formula for speed, distance and time?
Speed = distance ÷ time, distance = speed × time and time = distance ÷ speed. Use matching units: miles with hours for mph, kilometers with hours for km/h. 150 miles in 2.5 hours is 150 ÷ 2.5 = 60 mph.
How do I enter the time?
Type hours and minutes with a colon, like 2:30 for two and a half hours, or add seconds, like 0:45:30. A single number counts as hours, so 1.5 is an hour and a half. You can also write 2h 30m or 90 min.
How do I convert mph to km/h?
Multiply by 1.609344, the number of kilometers in a mile. 60 mph is about 96.56 km/h. To go from km/h to mph, divide by 1.609344: 100 km/h is about 62.14 mph. The calculator shows both, plus meters per second and knots.
How do I calculate average speed with stops?
Divide the total distance by the total time, including the stops. Driving 300 miles in 5 hours of driving with 45 minutes of breaks gives 300 ÷ 5.75 = 52.17 mph average, not 60. If you want the speed while moving, leave the stops out of the time.
What is a knot?
A knot is one nautical mile per hour and is used at sea and in aviation. A nautical mile is exactly 1,852 meters, a little longer than a regular mile, so 1 knot is 1.852 km/h or about 1.15 mph.