Speed, distance and time calculator
Speed:
On the graph, the slope of the line is the speed: the steeper it is, the faster. Move the time control to see where the dot is.
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Calculation:
This calculator solves the uniform motion equation, v = d ÷ t: enter any two of the three quantities and you get the third. You can work with speed in m/s, km/h or mph, distance in m, km or miles, and time in seconds, minutes or hours, without converting anything by hand. It also finds the average speed of a trip made of two legs at different speeds.
A dot moves along a track and the distance against time graph shows a straight line whose slope is the speed. Below you will find the formulas, worked examples and tables.
How to use the speed, distance and time calculator
Step 1: Choose what to find: Speed, Distance, Time or Two-leg trip.
Step 2: Enter the other two quantities and pick the unit of each. The field being solved is shaded and fills itself in.
Step 3: Click Calculate or press Enter. The result appears in the unit you picked and in other units too.
Step 4: Watch the track and the graph. The Time control moves the dot and shows the distance covered at each moment.
Uniform motion formulas
In uniform motion the speed does not change, so distance grows in proportion to time:
| v = d ÷ t d = v × t t = d ÷ v |
The units have to be compatible. The calculator converts everything to meters and seconds with these equivalences: 1 km = 1000 m, 1 mile = 1609.344 m (exact), 1 min = 60 s, 1 h = 3600 s, 1 km/h = 1 ÷ 3.6 m/s and 1 mph = 0.44704 m/s (exact).
For a trip in several legs, the average speed is the total distance divided by the total time, not the mean of the speeds:
| v average = (d1 + d2) ÷ (d1 ÷ v1 + d2 ÷ v2) |
Only when both legs take the same time is the average speed the plain mean of the two speeds. If they cover the same distance, the slow leg counts more because it takes longer.
Speed, distance and time examples
Example 1: The speed of a car
A car covers 150 km in 2.5 hours. We convert to meters and seconds and divide:
v = 150000 ÷ 9000 ≈ 16.67 m/s
That is 60 km/h. In km/h you get it directly: 150 ÷ 2.5 = 60.
Example 2: How far a cyclist rides
A cyclist rides at 18 km/h for 40 minutes. With 18 km/h = 5 m/s and 40 min = 2400 s:
d = 5 × 2400 = 12000 m
The cyclist covers 12 km.
Example 3: The time of a run
A person runs at 3 m/s. How long to cover 10 km? The 10 km are 10000 m:
t = 10000 ÷ 3 ≈ 3333.33 s
That is 55 min 33 s.
Example 4: A trip in two legs
A trip has 60 km at 30 km/h (2 hours) and then 60 km at 60 km/h (1 hour). The plain mean of the speeds would be 45 km/h, but the average speed is:
v = (60 + 60) ÷ (2 + 1) = 120 ÷ 3 = 40 km/h
The average speed is 40 km/h, lower than 45 km/h, because you spent more time going slowly.
Speed unit equivalences
What each unit equals in the other two:
| Unit | In m/s | In km/h | In mph |
|---|---|---|---|
| 1 m/s | 1 | 3.6 | 2.237 |
| 1 km/h | 0.2778 | 1 | 0.6214 |
| 1 mph | 0.447 | 1.609 | 1 |
Time to travel 100 km
| Speed (km/h) | Time (h) | Time (h, min, s) |
|---|---|---|
| 30 | 3.333 | 3 h 20 min |
| 50 | 2 | 2 h |
| 60 | 1.667 | 1 h 40 min |
| 80 | 1.25 | 1 h 15 min |
| 100 | 1 | 1 h |
| 120 | 0.8333 | 50 min |
Frequently asked questions
How do you find speed from distance and time?
Divide distance by time, v = d ÷ t. With 150 km in 2.5 h: 150 ÷ 2.5 = 60 km/h, which is 16.67 m/s.
What is the difference between average speed and the mean of the speeds?
Average speed uses the total distance and the total time. The mean of the speeds matches it only when the legs last the same time. Example 4 shows it: 45 km/h against 40 km/h.
How do I convert km/h to m/s?
Divide by 3.6, because 1 km = 1000 m and 1 h = 3600 s. To go from m/s to km/h, multiply by 3.6. You can also use the km/h to m/s calculator.
What is uniform motion?
Motion in a straight line at constant speed. Its distance against time graph is a straight line starting at the origin.
Can I use it for cars or trains that change speed?
Only if you split the trip into legs of constant speed, as in the two-leg mode. For acceleration you need other formulas (constant acceleration).
Learn more
- Average velocity in physics with examples
- Velocity vs speed in physics
- Exercises on uniform linear motion
- Displacement vs time graph in physics
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