A speed calculator finds average speed by dividing distance by time. Formula: Speed = distance / time. Time must be positive. 100 miles in 2 hours is an average of 50 mph.
On this page
How to use the speed calculator
- Enter the distance.
- Enter the time in hours.
- Read the average speed.
How the speed calculator works
The speed calculator divides distance by time to give average speed:
- Speed = distance ÷ time
You enter a distance and a time in hours. The result is in your distance unit per hour, so miles give miles per hour and kilometres give kilometres per hour. Time must be greater than zero. The result shows up to 4 decimal places.
Speed calculator worked example
You drive 100 miles in 2 hours. The speed calculator returns 100 ÷ 2 = 50 mph. A marathon of 26.2 miles finished in 4 hours is an average of 6.55 mph. For a time in minutes, divide by 60 first: 45 minutes is 0.75 hours, so 5 km in 45 minutes is about 6.67 km/h.
| Distance | Time | Speed |
|---|---|---|
| 100 miles | 2 h | 50 mph |
| 26.2 miles | 4 h | 6.55 mph |
| 400 km | 6.5 h | 61.5385 km/h |
| 5 km | 0.75 h | 6.6667 km/h |
| 60 miles | 1 h | 60 mph |
Average versus instant speed
The result is an average over the whole trip. Your speed at any moment may be higher or lower. A trip with traffic and stops can average 35 mph even if you spent most of it at 60 mph. Physics calls the speed at a moment instantaneous speed; a speedometer shows it. Velocity is speed with a direction, so going around a track and back to the start gives zero average velocity but a positive average speed.
Finding distance or time instead
The same formula rearranges. Distance = speed × time, and time = distance ÷ speed. At 60 mph, 150 miles takes 2.5 hours. At 6.55 mph for 3 hours, you cover about 19.65 miles. The speed calculator handles the speed form; do the other two by hand or with the pace calculator for running.
Converting units
To change mph to km/h, multiply by 1.609344; to change km/h to mph, divide by the same number. Metres per second times 3.6 gives km/h. A speed of 50 mph is about 80.47 km/h, or 22.35 m/s. The speed converter does these conversions directly.
Speed and pace
Runners often use pace, the time per mile or kilometre, which is the reciprocal of speed. A speed of 6 mph equals a pace of 10 minutes per mile. To convert, divide 60 by the speed in mph to get minutes per mile.
Entering values
Use a positive distance and a positive time. The tool rejects a negative distance, since a negative speed has no meaning for a trip, and a distance of zero simply gives zero speed. Mixed times such as 1 hour 20 minutes should be entered as 1.3333 hours. Rounding the time too early can shift the result slightly, so keep a few decimals.
Everyday examples
A cyclist who rides 30 miles in 2.5 hours averages 12 mph. A train that covers 300 km in 2 hours averages 150 km/h. A walker who covers 3 miles in an hour moves at a typical brisk walking pace. A flight of 2,400 miles that takes 5 hours averages 480 mph, which includes taxiing, climbing and descending, so the cruising speed is higher. For a long road trip, include rest stops in the time if you want a realistic average for planning; leave them out if you want the average while moving.
Speed in physics
In physics, average speed is total distance divided by elapsed time, and it is a scalar with no direction. The SI unit is metres per second. When an object speeds up at a steady rate from rest, its average speed is half its final speed. Problems in textbooks often give distance in metres and time in seconds, so multiply the answer by 3.6 if you need km/h.
Tips
- Convert minutes to hours by dividing by 60.
- Keep the same distance unit throughout.
- Use the speed calculator result with time to plan arrival times.
- Remember the result is an average.
Related converters and calculators
Related calculators:
- Speed converter: units
- Pace calculator: running
- Distance calculator: distance
- Time calculator: time
Sources
OpenStax College Physics 2e, 2.3: Time, velocity and speed; NIST: SI units – length.
Formula and method
Speed = distance / time. Time must be positive.
Straight quotient. The form does not convert units; miles with hours yields mph-style speed.
Questions about this calculator
How do I calculate speed?
Divide distance by time.
What units does it use?
Your distance unit per hour.
How do I enter minutes?
Divide minutes by 60 to get hours.
How do I convert mph to km/h?
Multiply by 1.609344.
Is it average or instant speed?
Average speed.
Check the assumptions and units before relying on a result. Financial, tax and health estimates do not replace advice for your individual circumstances.
Report a calculation issue