Acceleration is how fast the speed itself changes
Velocity tells you how fast something moves. Acceleration tells you how quickly that velocity is changing — speeding up, slowing down, or holding steady. Take the change in velocity and divide by the time it took.
If a car goes from rest to 27.78 m/s (100 km/h) in 5 seconds, its acceleration is 27.78 ÷ 5 = 5.56 m/s². The unit, metres per second squared, reads as "metres per second, per second": every second, the speed climbs by that many m/s.
The same number from force and mass
You do not always know the velocities. If you know the push and the mass being pushed, Newton's second law gives the acceleration directly.
The heavier the object, the less it accelerates for the same force — which is why the calculator offers both routes to the same answer.
What the numbers feel like
| Situation | a (m/s²) |
|---|---|
| Elevator starting | ~1 |
| Car pulling away briskly | ~3 |
| Hard braking | ~8 |
| Gravity (g) | 9.8 |
| Rocket at liftoff | ~30 |
Comparing your result against gravity is the quickest gut check: an acceleration of 9.8 m/s² is exactly what you feel in free fall.
Reading the sign
A positive result means speeding up; a negative one means slowing down. Both come from the same formula — braking is just acceleration pointing the other way. The widget labels which is which as you type.
Frequently asked questions
How do you calculate acceleration?
Acceleration is the change in velocity divided by the time it takes: a = Δv ÷ Δt. For example, going from 0 to 100 km/h (27.78 m/s) in 5 seconds gives 27.78 ÷ 5 = 5.56 m/s². The result is in metres per second squared.
What is the acceleration formula in physics?
There are two common forms. From motion, a = Δv ÷ Δt, the velocity change over time. From forces, Newton's second law gives a = F ÷ m, force divided by mass. Both return the same acceleration in m/s².
What are the units of acceleration?
Metres per second squared (m/s²) in SI. One m/s² means the speed rises by 1 m/s every second. Gravity is about 9.8 m/s², often written as 1 g.
What does negative acceleration mean?
A negative sign means the object is slowing down: the final velocity is lower than the initial one. It is the same formula. Braking a car from 20 m/s to 0 in 4 seconds is −5 m/s².
How are force and acceleration related?
Through Newton's second law, F = m · a. Rearranged, a = F ÷ m: the same force gives a lighter object more acceleration. A 1000 N push on a 500 kg cart produces 2 m/s².