Speed, Distance and Time Calculator
Got two of the three quantities? The tool finds the third, converts the units by itself and shows all the math.
Educational use: results are estimates made for study and reference. Checking the answer and deciding what to do with it is the sole responsibility of whoever uses the tool. Read the legal notice.
On this page
- How to use the calculator
- The formula and its three versions
- Solved examples
- The triangle that helps you remember
- Reference speeds
- Where mistakes happen most
- Questions about speed and travel time
- What to use it for
- An average is not a speedometer
- How speed became a formula
- Vocabulary of motion
- Fun facts
- Keep going
How to use the calculator
- Choose what you want to find: average speed, distance or time.
- Fill in the other two quantities. Each distance or speed field has a unit selector: meters, kilometers or miles; km/h, m/s or mph.
- Time: type hours, minutes and/or seconds. For 1 h 30 min, enter 1 in hours and 30 in minutes. Decimals also work, like 1.5 in hours.
- Calculate. The result is shown in a common unit, with conversions to other units right below it.
The tool converts everything to meters and seconds internally, does the math and only then translates the result into the unit you will want to read. That is why mixing miles with minutes is no problem here.
The formula and its three versions
They are the same equation solved three different ways. The condition is that the speed is constant or that you are dealing with average speed.
Converting km/h and m/s
That 3.6 comes from 3,600 seconds in an hour divided by 1,000 meters in a kilometer. So 20 m/s is 72 km/h, and 90 km/h is 25 m/s.
Pace
Runners often talk about pace, which is the inverse of speed: the time spent per kilometer. At 12 km/h, the pace is 60 ÷ 12 = 5 minutes per kilometer. The calculator shows the pace when you ask for the speed.
Solved examples
1. The car trip
You drove 320 km in 4 hours. What is the average speed?
2. The Sunday run
Someone runs at 12 km/h for 45 minutes. What is the distance?
3. The marathon
How long does a marathon (42.195 km) take at a steady 10 km/h?
4. Changing units
A train moves at 20 m/s. What is that in km/h?
5. The round-trip trap
You go from A to B at 60 km/h and come back, along the same road, at 40 km/h. What was the average speed for the whole trip? Many people answer 50 km/h.
The average is 48 km/h, not 50. You spent more time at the lower speed, and that pulls the average down. In math, this is the harmonic mean.
The triangle that helps you remember
A classic trick: draw a triangle with D on top and V and T on the bottom. Cover the quantity you are looking for and what is left shows the calculation.
Reference speeds
| Who or what | km/h | m/s |
|---|---|---|
| Leisurely walk | 5 | 1.4 |
| Recreational run | 10 to 12 | 2.8 to 3.3 |
| City bicycle | 15 to 25 | 4.2 to 6.9 |
| Car on city streets | 40 to 60 | 11 to 17 |
| Car on a highway | 80 to 110 | 22 to 31 |
| Commercial airliner at cruising speed | about 900 | 250 |
| Sound in air (20 °C) | about 1,235 | 343 |
| Light in a vacuum | about 1.08 billion | 299,792,458 |
The values are approximate and serve as orders of magnitude. Speeds of people and vehicles vary a lot with conditions, fitness and traffic.
Where mistakes happen most
Mixing minutes with hours
Dividing 90 km by 45 minutes and calling it "2 km/h" is the classic mistake. 45 minutes is 0.75 h, and the correct speed is 120 km/h. If you are using the calculator, fill in the time in the right fields and it takes care of the conversions.
Treating decimal time as "hours and minutes"
1.5 hours is 1 hour and 30 minutes, not 1 hour and 50. Time is not decimal by nature: 1.25 h is 1 h 15 min.
Averaging the speeds
As in example 5, the average speed of a trip is not the simple average of the speeds of its legs, unless the times spent are equal. The right way is always to divide the total distance by the total time.
Confusing km/h with m/s
The difference is a factor of 3.6. 10 m/s is 36 km/h, not 10 km/h. In physics exams, the final unit usually calls for this conversion.
Ignoring stops and traffic
The average speed of a real trip includes the stops. If you want to estimate the time of a route, use a realistic average, not the maximum speed of the road.
Questions about speed and travel time
How do I calculate average speed?
Divide the total distance by the total time. 320 km in 4 hours gives 80 km/h.
How do I convert km/h to m/s?
Divide by 3.6. 72 km/h ÷ 3.6 = 20 m/s. In the other direction, multiply by 3.6.
How do I calculate the time of a trip?
Divide the distance by the average speed. 150 km at 100 km/h takes 1.5 hours, or 1 h 30 min.
How do I calculate the distance traveled?
Multiply the speed by the time, with the time in the same time unit as the speed. 60 km/h for 2 h equals 120 km.
Is 1.5 hours the same as 1 hour and 50 minutes?
No. 1.5 hours is 1 hour and 30 minutes, because 0.5 hour is half of 60 minutes. To convert the decimal part, multiply by 60.
What is pace and how do I convert it to speed?
Pace is the time per kilometer. To convert it to speed, divide 60 by the pace in minutes: 5 min/km corresponds to 60 ÷ 5 = 12 km/h.
Is average speed the average of the speeds?
Only if the times are equal. In general, it is the total distance divided by the total time, which can give a different result (in example 5, 48 km/h instead of 50).
How do I convert miles per hour to km/h?
Multiply by 1.609344. 60 mph is about 96.56 km/h.
Can I leave a time field blank?
Yes. Blank hours, minutes and seconds fields count as zero, and you must fill in at least one of them with a value greater than zero.
Does this tool work for acceleration?
No. It applies to constant or average speed. Motion with acceleration has other formulas.
What to use it for
- Trips: estimating the arrival time, or the speed needed to get there on time.
- Running and cycling: planning training and race pace, and converting between pace (min/km) and speed (km/h).
- School physics: uniform motion problems, meeting points of moving objects and unit conversion.
- Logistics: predicting delivery times and planning routes.
- Sports and games: the speed of balls, swimmers and rowers.
- Curiosity: how long light takes to travel from the Sun to the Earth (about 8 minutes and 20 seconds) or a plane to cross the Atlantic.
An average is not a speedometer
The tool calculates average speed. It does not replace a speedometer and does not take into account stops, traffic lights, hills, wind, current or acceleration. The calculated travel time is theoretical, and in real life it is usually longer.
Do not use the result to make safety decisions, such as the speed allowed on a road, braking distance or reaction time. In those cases, traffic rules and the guidance of qualified professionals apply. The conversions use exact factors (1 mile = 1,609.344 m), and the display is rounded.
Bottom line: this tool is educational. Results do not replace your own checking, and how you use them is entirely your responsibility. More details in the legal notice.
How speed became a formula
Measuring speed as "distance per time" seems obvious today, but it took Galileo, in the 17th century, to formalize uniform motion and show that falling motion was not what people had believed since Aristotle. He rolled balls down inclined planes, timed them with water clocks and concluded that the distance grows with the square of the time.
The km/h unit only became common with railways and, later, automobiles. In the International System of Units, the unit of speed is the meter per second, and the kilometer per hour is tolerated because it is practical for everyday life.
Vocabulary of motion
- Average speed
- The total distance traveled divided by the total time spent.
- Uniform motion
- Motion at constant speed, with no speeding up or slowing down.
- Distance
- The length of the path traveled, measured in meters, kilometers or miles.
- km/h and m/s
- Kilometers per hour and meters per second. 1 m/s = 3.6 km/h.
- Pace
- The time spent to cover one unit of distance, usually minutes per kilometer.
- Knot
- One nautical mile per hour (1.852 km/h).
- Harmonic mean
- A type of average suited to speeds when the distances of the legs are equal.
Fun facts
- Knot: a unit used in sea and air navigation. 1 knot equals 1 nautical mile per hour, or about 1.852 km/h. The name comes from an old rope with knots in it, thrown into the sea to measure speed.
- The speed of sound varies with temperature. It is about 343 m/s at 20 °C, but lower in cold air.
- Usain Bolt reached peaks of about 44 km/h in the 100 meters. His average, however, was a little over 37 km/h, because he has to accelerate at the start.