Calculators
Acceleration Calculator
Solve average acceleration, velocity, or time.
Acceleration Calculator tool
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About This Tool
Acceleration measures how quickly velocity changes with time. For a time interval, average acceleration is the change from initial velocity u to final velocity v divided by elapsed time t: a = (v − u)/t. This calculator solves that relationship in any direction, handles common velocity and time units, and keeps signed values so slowing down or motion along an opposite axis can be represented correctly. Calculations run locally in your browser.
How To Use It
- Choose whether to solve for average acceleration, initial velocity, final velocity, or elapsed time.
- Enter the known values. Use positive and negative velocity or acceleration consistently with the direction you define as positive.
- Select the velocity, time, acceleration, and result units you need. Acceleration inputs can use m/s², ft/s², or standard gravity g.
- Interpret the result as average acceleration over the interval; it does not prove acceleration was constant at every instant.
Examples
Speeding up
Changing from 0 to 20 m/s in 4 s gives a = (20 − 0)/4 = 5 m/s².
Slowing down
Changing from 20 m/s to 0 in 4 s gives -5 m/s² when the original direction is positive.
Kilometres per hour
Changing from 0 to 36 km/h in 2 s is a 10 m/s velocity change, so average acceleration is 5 m/s².
Find final velocity
Starting at 2 m/s with 3 m/s² average acceleration for 4 s gives v = 2 + 3×4 = 14 m/s.
Useful Notes
Average acceleration formula
Average acceleration is a = (v − u)/t, where u is initial velocity, v is final velocity, and t is elapsed time. Rearrangements are v = u + at, u = v − at, and t = (v − u)/a.
Direction and negative acceleration
Velocity and acceleration are signed quantities in one-dimensional motion. Negative acceleration does not always mean an object is slowing down; it means acceleration points in the negative direction of the coordinate axis you chose.
Units
The SI acceleration unit is metres per second squared (m/s²). The calculator converts km/h and mph velocities before applying the formula. Acceleration inputs and results can use m/s², ft/s², or standard gravity g.
Average versus instantaneous acceleration
This relationship gives average acceleration over an interval from two velocities and elapsed time. If acceleration varies during the interval, instantaneous acceleration at a particular moment requires more information about velocity as a function of time.
Model limitations
The calculator treats motion as one-dimensional and uses signed scalar components along one chosen axis. It does not calculate distance, vector direction in two or three dimensions, variable-acceleration curves, or relativistic motion.
FAQ
What is acceleration?
Acceleration is the rate at which velocity changes with time. Because velocity includes direction, a change in direction can also be acceleration.
Can acceleration be negative?
Yes. The sign indicates direction relative to the coordinate axis you chose. Whether the object speeds up or slows down depends on both velocity and acceleration signs.
Is deceleration always negative?
No. Deceleration means speed is decreasing. Its acceleration sign depends on which direction you defined as positive.
What does 1 g mean?
Standard gravity is defined as 9.80665 m/s². It is commonly used as an acceleration comparison unit.