How to use the speed calculator
Choose what you want to find: speed, distance or travel time. The form then asks only for the two values you know. Each value has its own unit, so you can enter kilometers with minutes or miles with seconds without converting anything first.
The result shows the answer and the same value in other units. You also get a reverse check that plugs the answer back into the formula, and a table of times for standard distances at that speed.
- Pick Speed, Distance or Travel time as the value to calculate.
- Enter the two values you know.
- Check the unit next to each one (miles, km, meters, feet; seconds, minutes, hours, days; mph, km/h, m/s, ft/s, knots).
- Press Calculate and read the answer and the unit conversions.
- Use the pace rows and benchmark table if you're working with a run, walk or ride.
Speed, distance and time formula
One relationship covers all three questions. Speed is distance over time, and the other two are just rearrangements. The units have to match: miles with hours gives mph, meters with seconds gives m/s. The calculator converts everything to meters and seconds first, solves, and then converts back.
Speed = distance / timeDistance = speed x timeTime = distance / speedPace = time / distance
| You want | You know | Formula |
|---|---|---|
| Average speed | Distance and time | speed = distance / time |
| Distance | Speed and time | distance = speed x time |
| Travel time | Distance and speed | time = distance / speed |
Worked examples
Each example below uses the same formula with a different unknown. Minutes become hours by dividing by 60, so 45 minutes is 0.75 hours and 25 minutes is about 0.4167 hours.
| Question | Known values | Math | Answer |
|---|---|---|---|
| Road trip average speed | 100 mi in 2 h | 100 / 2 | 50 mph (80.4672 km/h) |
| Distance at a steady speed | 72 km/h for 45 min | 72 x 0.75 | 54 km |
| Time for a route | 10 km at 12 km/h | 10 / 12 | 50 minutes |
| 5K running speed | 5 km in 25 min | 5 / (25 / 60) | 12 km/h (5:00 per km) |
Average speed calculator: stops and round trips
Average speed is total distance divided by total time. Include stops if you want the whole-trip average. A 100-mile trip that takes 2 hours, including a 20-minute stop, averages 50 mph. Using only the 100 minutes of moving time gives 60 mph. Both are right; they answer different questions.
Don't average the speeds themselves. Drive 60 miles out at 30 mph and 60 miles back at 60 mph and the average isn't 45 mph. The trip out takes 2 hours and the trip back takes 1, so it's 120 miles in 3 hours: 40 mph. Add up distances and times, then divide.
Pace calculator: speed to minutes per mile
Runners and walkers usually think in pace, which is time per distance. The calculator shows pace per mile and per kilometer next to every speed. At 12 km/h, a kilometer takes 5:00 and a mile about 8:03.
The benchmark table then applies your speed to 100 m, 1 km, 1 mile, 5K, 10K, a half marathon and a marathon. Those times assume you hold the same speed the whole way, which few people do over long distances.
Speed unit conversions
NIST defines 1 mph as exactly 0.44704 m/s and 1.609344 km/h. A knot is one nautical mile per hour, about 0.5144 m/s. To turn mph into km/h, multiply by 1.609344. To go the other way, divide by 1.609344 or multiply by about 0.621371.
| Starting rate | m/s | km/h | mph |
|---|---|---|---|
| 1 m/s | 1 | 3.6 | 2.236936 |
| 1 mph | 0.44704 | 1.609344 | 1 |
| 1 km/h | 0.2777778 | 1 | 0.621371 |
| 1 knot | 0.5144444 | 1.852 | 1.150779 |
| 1 ft/s | 0.3048 | 1.09728 | 0.681818 |
Mistakes that give the wrong answer
Decimal hours trip people up most. 1 hour 30 minutes is 1.5 hours, but 1.30 hours is only 1 hour 18 minutes. If your time has minutes in it, pick minutes as the unit instead.
Also check that distance and time cover the same stretch, and that you're using the route distance, not a straight line on a map. The calculator gives average speed along a path. It doesn't work out velocity with direction, acceleration, or the speed at any one moment, and it isn't evidence of legal speed.
Sources
These references back up the speed formula, the difference between average and instantaneous speed, and the unit factors on this page.