What is the average speed?
Enter any two of distance, time and average speed. The calculator finds the third and converts between units for you.
- Average speed
- 60 mph
Covering 150 mi in 2.5 h is an average speed of 60 mph.
Average speed: 60 mph. Covering 150 mi in 2.5 h is an average speed of 60 mph.
How to calculate
Computes average speed from distance and time, or the distance covered or the time taken from the other two, in any units.
Example with the default inputs (Distance 150 mi, Time 2.5 h): Covering 150 mi in 2.5 h is an average speed of 60 mph.
Formula: speed = distance ÷ time; distance = speed × time; time = distance ÷ speed.
- The speed is the average over the whole trip. It says nothing about the speed at any one moment.
- Units are converted exactly: 1 mi = 1,609.344 m, 1 ft = 0.3048 m, 1 nautical mile = 1,852 m (NIST SP 811).
Worked examples
Each example is checked against the calculator on every build.
- Distance 150 mi, Time 2.5 h gives Average speed 60 mph.Source: hand calculation in content.mdx: 150 mi ÷ 2.5 h = 60 mph = 60 × 1,609.344 m ÷ 3,600 s = 26.8224 m/s (NIST SP 811: 1 mi = 1,609.344 m)
- Average speed 62.137 mph, Time 0.75 h gives Distance 46.6 mi.Source: hand calculation in content.mdx: 100 km/h × 0.75 h = 75 km
- Distance 26.22 mi, Average speed 11.185 mph gives Time 2.344 h.Source: hand calculation in content.mdx: 42,195 m ÷ 5 m/s = 8,439 s = 2 h 20 min 39 s
How it works
Average speed is the distance travelled divided by the time taken:
- speed = distance ÷ time
- distance = speed × time
- time = distance ÷ speed
The calculator converts every value to meters and seconds first, solves, and converts the answer back to the unit you pick. The conversions are exact: 1 mile = 1,609.344 m, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 nautical mile = 1,852 m, 1 hour = 3,600 s. So 1 mph = 0.44704 m/s and 1 km/h = 1 ÷ 3.6 m/s.
Assumptions
- The answer is the average over the whole distance. It includes any stops.
- Distance, time and speed are all greater than zero.
Worked examples by hand
150 miles in 2 hours 30 minutes. 2 h 30 min = 2.5 h. Speed = 150 ÷ 2.5 = 60 mph. In SI units: 150 × 1,609.344 = 241,401.6 m and 2.5 × 3,600 = 9,000 s, so 241,401.6 ÷ 9,000 = 26.8224 m/s.
100 km/h for 45 minutes. 45 min = 0.75 h. Distance = 100 × 0.75 = 75 km.
A marathon at 5 m/s. The marathon is 42.195 km = 42,195 m. Time = 42,195 ÷ 5 = 8,439 s = 2 h 20 min 39 s.
Other questions people ask
What is the formula for speed?
Average speed = distance ÷ time. For example, 150 miles in 2.5 hours is 150 ÷ 2.5 = 60 miles per hour.
How do I work out distance from speed and time?
Multiply them: distance = speed × time. At 100 km/h for 45 minutes (0.75 h) you cover 100 × 0.75 = 75 km. Put the time in the same unit as the speed first (hours for km/h or mph).
How do I work out the time from distance and speed?
Divide the distance by the speed: time = distance ÷ speed. A 42.195 km marathon at 5 m/s takes 42,195 ÷ 5 = 8,439 seconds, which is 2 hours, 20 minutes and 39 seconds.
What is the difference between speed and average speed?
Speed at one moment is what a speedometer shows. Average speed is the total distance divided by the total time, including slow parts and stops. This calculator gives the average speed.
How do I convert mph to km/h?
Multiply by 1.609344, because one mile is exactly 1,609.344 meters. 60 mph is 96.56 km/h. Pick another unit next to the speed box to see it converted.