What is instantaneous velocity?

Instantaneous velocity is the velocity at a single moment in time, as opposed to average velocity over an interval. A speedometer shows instantaneous speed. Mathematically, it is the derivative of position with respect to time.

What is terminal velocity?

Terminal velocity is the constant speed reached when air resistance equals gravitational force. For a human skydiver it is about 55 m/s (120 mph) in a spread-eagle position and 90 m/s (200 mph) in a head-down dive.

Can velocity be negative?

Yes. In physics, negative velocity means motion in the opposite direction of the chosen positive direction. If rightward is positive, a car moving left has negative velocity. The sign conveys direction.

What is escape velocity?

Escape velocity is the minimum speed needed to permanently leave a gravitational field. For Earth it is 11.2 km/s (40,320 km/h). It depends on the mass and radius of the celestial body: v = sqrt(2GM/R).

Velocity Calculator

Calculate velocity, distance, or time — v = d / t

Velocity Calculator

Calculate velocity from distance and time

Velocity Calculator

v = d / t

Distance (m)

Time (s)

Formula

v = d / t

What Is Velocity?

Velocity is the rate of change of position — how fast an object moves in a specific direction. Unlike speed, which is a scalar quantity with magnitude only, velocity is a vector with both magnitude and direction. It is measured in meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph). The average velocity over a journey equals the total displacement divided by the total time elapsed.

This calculator solves for any variable in the core velocity equation: velocity, distance, or time. Simply enter the two known values and the calculator finds the third. It also supports unit conversions between m/s, km/h, and mph, making it practical for physics homework, road-trip planning, sports timing, and engineering analysis.

How to Use the Velocity Calculator

Select what you want to calculate — velocity, distance, or time.
Enter the two known values in their respective fields.
Select the appropriate units for each value.
Click Calculate to see the result along with automatic unit conversions.

Velocity Formulas & Unit Conversions

v = d / t   (velocity = distance / time)
d = v × t   (distance = velocity × time)
t = d / v   (time = distance / velocity)

Unit conversions:
  1 m/s  = 3.6 km/h    = 2.237 mph
  1 km/h = 0.2778 m/s  = 0.6214 mph
  1 mph  = 1.609 km/h  = 0.4470 m/s

Average velocity (constant acceleration):
  v_avg = (v_initial + v_final) / 2

Speed is the magnitude of velocity and is always a positive number. Velocity can be negative when an object moves in the opposite of the chosen positive direction. Note that average velocity does not equal average speed whenever the direction of motion changes during the trip.

Worked Examples

Car trip: 150 km in 2 hours

v = d / t = 150 km / 2 h = 75 km/h. Converting: 75 km/h × 0.6214 = 46.6 mph, or 75 / 3.6 = 20.83 m/s.

Runner at 3 m/s for 10 seconds

d = v × t = 3 m/s × 10 s = 30 m. At that pace, the runner covers one kilometre in about 333 seconds (5 min 33 s).

Speed of light

Light travels at 299,792,458 m/s in a vacuum — approximately 1,079,252,848 km/h or 670,616,629 mph. It covers the Earth-Moon distance (~384,400 km) in about 1.28 seconds.

Frequently Asked Questions

What is the difference between speed and velocity?▾

Speed is a scalar — it only tells you how fast something is moving (e.g., 60 km/h). Velocity is a vector — it tells you how fast and in what direction (e.g., 60 km/h north). Two cars can have the same speed but different velocities if they travel in different directions.

What does average velocity mean?▾

Average velocity is the total displacement (change in position from start to finish) divided by the total time. If you drive 100 km east and then 100 km back west, your displacement is zero and your average velocity is 0 m/s — even though your average speed was not zero.

How do I convert m/s to km/h?▾

Multiply by 3.6. For example, 10 m/s × 3.6 = 36 km/h. To go the other way, divide by 3.6: 36 km/h / 3.6 = 10 m/s. This factor comes from converting 1 metre to 0.001 km and 1 second to 1/3600 of an hour.

What is relative velocity?▾

Relative velocity is the velocity of one object as observed from another moving object. If two cars travel in the same direction at 80 km/h and 60 km/h, their relative velocity is 20 km/h. If they travel toward each other, their relative velocity is 80 + 60 = 140 km/h. This concept is essential in navigation, collision analysis, and special relativity.

What is the speed of sound?▾

The speed of sound in dry air at 20 °C is approximately 343 m/s (1,235 km/h or 767 mph). It varies with the medium and temperature — sound travels faster in warmer air and much faster in liquids and solids. In water it is about 1,480 m/s; in steel, around 5,960 m/s.