This acceleration calculator finds acceleration, final velocity or time using a = (vf − vi) ÷ t. Enter the values you know — it handles speed units (m/s, km/h, mph) and shows the result in m/s² and g.
What Is Acceleration?
Acceleration is the rate at which velocity changes — speeding up, slowing down, or changing direction all count. Its unit, m/s², reads “meters per second, per second”: how much velocity changes each second. Acceleration is where dynamics begins, because Newton’s second law ties it directly to force (see our Force Calculator). This calculator is part of our Physics Calculators collection.
The Acceleration Formula
a = (vf − vi) ÷ t
Worked examples (verified):
- A car going 0 → 100 km/h (27.78 m/s) in 8 seconds: a = 27.78 ÷ 8 = 3.47 m/s² — about 0.35 g.
- 0 → 60 mph in 6 seconds: 4.47 m/s². Sports cars launch near 1 g; a family sedan manages about half that.
- Falling objects on Earth: a = 9.81 m/s² exactly defines 1 g — the acceleration your body is built around.
Acceleration Feels and Numbers
| Situation | Acceleration |
|---|---|
| Family car, gentle start | ~2 m/s² (0.2 g) |
| Family car, full throttle | ~4–5 m/s² |
| Hard braking | ~8 m/s² (0.8 g) |
| Free fall on Earth | 9.81 m/s² (1 g) |
| Fighter jet catapult launch | ~40 m/s² (4 g) |
| Car crash into a barrier | 200+ m/s² (20+ g) |
Negative acceleration is deceleration — the calculator returns it with a minus sign, which is physically correct: acceleration is a vector. Pair a velocity change with the energy it represents in our Kinetic Energy Calculator.
Related Tools
- Force Calculator — F = ma from acceleration
- Kinetic Energy Calculator
- Physics Calculators — the full collection
Frequently Asked Questions
How do I calculate acceleration?
Subtract the initial velocity from the final velocity and divide by the time taken: a = (v_f − v_i) ÷ t. Keep units consistent — meters per second and seconds give m/s².
What is the difference between acceleration and velocity?
Velocity is how fast something moves (with direction); acceleration is how quickly that velocity itself changes. You can have zero velocity and nonzero acceleration — at the top of a thrown ball’s flight, for an instant.
What does 1 g mean?
An acceleration of 9.81 m/s² — Earth’s gravitational acceleration. Pilots, astronauts and roller-coaster riders all measure their experience in g.
Can acceleration be negative?
Yes — negative acceleration means velocity is decreasing in the chosen direction (braking) or the direction convention is reversed. Physics treats it as acceleration with a sign, not a different quantity.
How fast do objects accelerate when falling?
At 9.81 m/s² on Earth regardless of mass (ignoring air resistance) — on the Moon about 1.62 m/s², on Mars about 3.71 m/s².
Is this acceleration calculator free?
Yes — free, instant, no sign-up.