How to use the speed calculator
- Choose what to calculate: speed, distance or time.
- Enter the distance and pick kilometers, miles, meters, feet or nautical miles.
- Enter the speed in km/h, mph, m/s, knots or ft/s.
- Enter the time in hours, minutes and seconds. You can type 90 minutes or 1 hour and 30 minutes; both work.
- The unit beside the quantity you are solving for sets how the answer is shown. The results also list the speed in every unit and the pace per kilometer and per mile.
The speed formula
Average speed is distance divided by time. Rearranging gives the other two:
These conversions are exact by definition: the international mile is 1,609.344 m, the foot 0.3048 m and the nautical mile 1,852 m. The calculator converts everything to meters and seconds, solves, and converts back.
Worked example
The defaults are 100 km covered in 1 hour 15 minutes:
- Time in hours: 1 + 15 ÷ 60 = 1.25 h
- Speed: 100 km ÷ 1.25 h = 80 km/h
- In mph: 80 ÷ 1.609344 = 49.71 mph
- In m/s: 80 ÷ 3.6 = 22.22 m/s
- In knots: 80 ÷ 1.852 = 43.20 kn
- Pace: 45 seconds per kilometer, or 1 minute 12 seconds per mile
Switch to distance and enter 60 mph for the same 1 hour 15 minutes: 60 × 1.25 = 75 miles. Switch to time and 100 km at 80 km/h takes 1 h 15 min.
Common speeds for reference
| Speed | km/h | mph | m/s |
|---|---|---|---|
| Walking | 5 | 3.1 | 1.4 |
| Easy running | 10 | 6.2 | 2.8 |
| Cycling | 20 | 12.4 | 5.6 |
| City speed limit (30 mph) | 48.3 | 30 | 13.4 |
| Highway (65 mph) | 104.6 | 65 | 29.1 |
| Speed of sound (air, 20 °C) | 1,235 | 767 | 343 |
Mistakes to avoid
Decimal hours are not minutes. 1.15 hours is 1 hour 9 minutes, not 1 hour 15 minutes, because 0.15 × 60 = 9. Enter hours and minutes in their own boxes to avoid this. Average is not top speed. A trip of 100 km in 1 hour 15 minutes averages 80 km/h even if you sat at 110 km/h on the highway and stopped at lights in town. Average speed over two legs is not the average of the two speeds. Driving 60 km at 60 km/h and another 60 km at 120 km/h takes 1.5 hours for 120 km, an average of 80 km/h, not 90. Weight each speed by the time spent at it, or just enter the total distance and total time.
For the energy side of motion, such as the power needed to reach a speed, see the horsepower calculator.
Frequently asked questions
How do I calculate speed?
Divide the distance by the time taken. If you cycle 30 km in 1 hour 30 minutes, your average speed is 30 ÷ 1.5 = 20 km/h, or 12.4 mph. Make sure the time is in hours if you want km/h or mph.
How do I convert km/h to mph?
Divide by 1.609344, or multiply by about 0.6214. So 100 km/h is 62.1 mph. To go from mph to km/h, multiply by 1.609344: 60 mph is 96.6 km/h.
What is a knot?
A knot is one nautical mile per hour, 1.852 km/h or about 1.151 mph. It is used at sea and in aviation because a nautical mile corresponds to one minute of latitude.
How do I work out travel time?
Divide the distance by the speed. A 250-mile trip at an average of 50 mph takes 250 ÷ 50 = 5 hours. Add time for stops, since your average speed over a whole trip is usually below your cruising speed.
Related calculators
- Horsepower Calculator — Horsepower from torque and rpm, or from force, distance and time, plus hp, PS and kW conversions.
- Fuel Cost Calculator — The fuel cost of a road trip from distance, fuel economy and price, with round trips and cost per person.
- Pace Calculator — Running pace, finish time or distance in km or miles, with race presets, splits and equivalent race times.
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