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Velocity Calculator
Solve the velocity equation for whichever quantity your homework asks for: velocity from displacement and time, displacement from velocity and time, or time from displacement and velocity. A fourth mode finds final velocity from initial velocity, acceleration and time. Enter values in any units — meters, miles, seconds, hours — and the answer comes back in SI with mph alongside.
- Velocity
- 10.44 m/s
- Displacement
- 100 m
- Time
- 9.58 s
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Your recent calculations
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Formula
How to use it
- Choose what you are solving for.
- Enter the known values, picking the unit next to each box.
- Read the answer in m/s, m or s; switch the unit on any result row to convert it.
- Show your working with the formula above, converting to SI units first as most courses expect.
Worked examples
A 100 m sprint in 9.58 s: v = 100 ÷ 9.58
- Answer
- 10.44 m/s (23.35 mph)
- Velocity
- 10.44 m/s
60 miles in 1.5 hours, worked in SI: 96,560.64 m ÷ 5,400 s
- Answer
- 17.88 m/s (40 mph)
- Velocity
- 17.88 m/s
Displacement at 25 m/s for 4 s: Δx = 25 × 4
- Answer
- 100 m (328.08 ft)
- Displacement
- 100 m
Time to walk 1,500 m at 2.5 m/s: t = 1,500 ÷ 2.5
- Answer
- 600 s (10 minutes)
- Time
- 600 s
A ball dropped from rest after 2 s: v = 0 + 9.81 × 2, Δx = ½ × 9.81 × 2²
- Answer
- 19.62 m/s (43.89 mph)
- Velocity
- 19.62 m/s
- Displacement
- 19.62 m
Walking 30 m back the way you came in 20 s: v = −30 ÷ 20
- Answer
- -1.5 m/s (-3.355 mph)
- Velocity
- -1.5 m/s
Velocity versus speed
Speed is how fast something moves; velocity is speed in a stated direction, so it can be negative. A runner who finishes a 400 m lap back at the start has an average speed of 400 m ÷ time but an average velocity of zero, because the displacement is zero.
Enter a negative displacement or velocity for motion in the opposite direction to the one you call positive.
Common mistakes
Mixing units is the most common error: 60 miles in 90 minutes is 40 mph, not 0.67. Convert to meters and seconds before dividing, or let the unit menus do it.
v = Δx ÷ t gives the average velocity over the interval. If the object speeds up or slows down along the way, its velocity at any instant can be quite different; use the final-velocity mode when the acceleration is constant.
Questions people ask
How do you calculate velocity?
Divide displacement by time. 100 m in 9.58 s is 100 ÷ 9.58 = 10.44 m/s, about 23.35 mph.
How do you find final velocity?
Use v = v₀ + a × t. A ball dropped from rest falls for 2 s at 9.81 m/s², so v = 0 + 9.81 × 2 = 19.62 m/s, having fallen 19.62 m.
What is 10 m/s in mph?
About 22.37 mph, since 1 mph is exactly 0.44704 m/s. In km/h it is 36.
Can velocity be negative?
Yes. A negative velocity means motion in the direction you defined as negative. Walking 30 m back the way you came in 20 s is −1.5 m/s.