Velocity Calculator
Free velocity calculator: enter distance and time to find average velocity (v = d/t), or solve for distance, time, or acceleration with consistent units.
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Velocity calculator at a glance#
A velocity calculator finds how fast something moves in a given direction. Average velocity is displacement divided by time, written v = d / t. So an object that covers 100 meters in 20 seconds has a velocity of 5 meters per second (100 / 20 = 5).
Velocity is a vector, so it carries a direction, while speed is the same number without direction. The result above is an average velocity over the whole interval. Instantaneous velocity is the value at a single moment, which the calculator handles when you also enter acceleration and time.
| Quantity | Formula | Example |
|---|---|---|
| Average velocity | v = d / t | 100 m / 20 s = 5 m/s |
| Distance | d = v × t | 5 m/s × 20 s = 100 m |
| Time | t = d / v | 100 m / 5 m/s = 20 s |
| m/s to km/h | multiply by 3.6 | 5 m/s × 3.6 = 18 km/h |
To convert units, multiply meters per second by 3.6 to get kilometers per hour, so 5 m/s is 18 km/h. Enter your distance and time in the calculator above for the exact velocity, and switch the unknown to solve for distance, time, or acceleration. Use consistent units, since mixing meters with hours gives a wrong result.
Types of velocity#
Average velocity is the displacement divided by the time over an interval. Instantaneous velocity is the value at a single moment. Relative velocity describes how fast one object moves compared with another that is also moving. All three are vectors, so each carries a direction as well as a magnitude.
Velocity with constant acceleration#
When an object speeds up or slows down at a steady rate, final velocity is the starting velocity plus acceleration times time: v = u + a·t. Rearrange it to find any single unknown: u = v − a·t, a = (v − u) / t, or t = (v − u) / a.
Worked examples#
Car over a distance#
A car that travels 150 km in 2 hours has an average velocity of 150 / 2 = 75 km/h.
Runner on a track#
A sprinter covering 400 m in 50 s runs at 400 / 50 = 8 m/s.
Skateboarder accelerating from rest#
A skateboarder starts at 0 m/s and reaches 5 m/s in 10 s. The acceleration is a = (5 − 0) / 10 = 0.5 m/s².
Keep units consistent#
Use the same system for every input. Pair meters with seconds for m/s, or kilometers with hours for km/h. Mixing meters with hours produces a wrong answer. To convert, multiply m/s by 3.6 to get km/h, or divide km/h by 3.6 to get m/s.
FAQ#
How do I calculate initial velocity?#
If you know the final velocity, acceleration, and time, use u = v − a·t. For v = 20 m/s, a = 2 m/s², and t = 5 s, u = 20 − 2 × 5 = 10 m/s.
What is the difference between average and instantaneous velocity?#
Average velocity is total displacement divided by total time. Instantaneous velocity is the value at one exact moment, which matters when the speed keeps changing.
How do I find final velocity from acceleration?#
Add the change to the start: v = u + a·t. From 10 m/s with a = 3 m/s² over 4 s, v = 10 + 3 × 4 = 22 m/s.
Why is velocity a vector?#
Velocity has both a size and a direction, so 5 m/s north differs from 5 m/s south. Speed is the size alone, with no direction.
What units should I use?#
Common pairs are meters per second (m/s) and kilometers per hour (km/h). Keep displacement and time in matching units so the result is correct.
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