Acceleration Calculator
Calculate average acceleration from initial velocity, final velocity and time (a = Δv/t) in m/s², with a worked example and a comparison with g.
Results
Acceleration
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Formula / how it works
a = (v₁ − v₀) ÷ t, with velocities in m/s and time in seconds giving m/s². One standard gravity g = 9.80665 m/s².
Detailed guide
What it is, how to use it, how to read the numbers, common mistakes, a worked example, formulas, and FAQs.
What this calculator is
Acceleration is how quickly velocity changes. If a car speeds up from rest to 20 m/s in 4 seconds, its average acceleration is 5 m/s². A negative value means the object is slowing down, often called deceleration. This calculator uses the definition a = (final velocity − initial velocity) ÷ time. Students meet this in the first weeks of kinematics, while engineers and drivers use it to describe launches, braking and lift-off. The tool gives the average over the interval and assumes motion in a straight line; it does not model changing acceleration, drag or direction changes.
When to use / who it helps
- You know the start and end velocities and the time between them.
- You are solving a kinematics problem and need the acceleration before using other equations.
- You want to compare a vehicle's 0 to 100 km/h time with an acceleration in m/s².
- You are checking braking performance from a stopping time.
- You want to express acceleration in multiples of g.
How to use
Steps
- Enter the initial velocity in m/s; use 0 for starting from rest.
- Enter the final velocity in m/s.
- Enter the time elapsed in seconds.
- Read the acceleration in m/s².
- To convert from km/h, divide by 3.6 before entering.
- Divide the result by 9.80665 to compare with standard gravity.
How to interpret results
- Positive acceleration means velocity is increasing in the chosen direction; negative means decreasing.
- The result is the average over the interval, not necessarily constant throughout.
- 5 m/s² is about 0.5 g, noticeable but comfortable for a car.
- Free fall near the Earth's surface is about 9.8 m/s² without air resistance.
- If the time is very short, small timing errors change the result a lot.
Common mistakes & gotchas
- Entering km/h or mph values without converting to m/s.
- Using total speed change over a time that includes a constant-speed period.
- Forgetting that deceleration is negative acceleration.
- Entering time in minutes while velocities are in m/s.
- Applying constant acceleration formulas when acceleration changes.
Worked example
Worked example — 0 to 20 m/s in 4 seconds
- Change in velocity: 20 − 0 = 20 m/s.
- Divide by time: 20 ÷ 4 = 5 m/s².
- In g units: 5 ÷ 9.80665 ≈ 0.51 g.
- A car going 0 to 100 km/h (27.78 m/s) in 8 s has a = 27.78 ÷ 8 ≈ 3.47 m/s², about 0.35 g.
Result: An average acceleration of 5 m/s² (about 0.5 g).
To load the form's own demo values, tap Try example above the Calculate button.
How to calculate / formula
a = (v₁ − v₀) ÷ t, with velocities in m/s and time in seconds giving m/s². One standard gravity g = 9.80665 m/s².
Frequently asked questions
What is the formula for acceleration?
Average acceleration equals change in velocity divided by time, a = Δv/t.
What unit is acceleration measured in?
Metres per second squared (m/s²) in SI units.
Can acceleration be negative?
Yes. It indicates slowing down in the positive direction, or speeding up in the opposite direction.
How do I convert km/h to m/s?
Divide by 3.6.
How does this relate to g-force?
Divide the acceleration by 9.80665 to express it in multiples of standard gravity.
Is this instantaneous acceleration?
No. It is the average over the entire time interval.
Textbook formulas under ideal assumptions. For safety-critical, structural, or regulated work, verify with a qualified engineer and the governing standards. Full disclaimer