From rest to 100 km/h in 10 seconds
ā = (v − v₀) ÷ t
100 km/h is exactly 250/9 m/s. Dividing that velocity change by 10 s gives 25/9 m/s², displayed as ≈ 2.777778 m/s². This average does not describe every moment of the trip.
Motion along one axis
Acceleration Calculator
Find average acceleration from two velocities and elapsed time, or find a velocity when acceleration stays constant.
Calculate acceleration or velocity
Average acceleration
Enter the known values and elapsed time, then select Calculate.
- SI equivalent
- Velocity change
- Elapsed time
- Formula
- Model
Calculation steps
≈ marks display rounding. Calculations run in your browser. Press Enter to calculate. Successful results appear in this tab's Recent calculations.
Three motion examples
20 m/s with −2 m/s² for 6 seconds
v = v₀ + a × t
The change is −12 m/s, so the final velocity is 8 m/s. The object still moves in the positive direction at the end, with a lower speed.
Ending at −3 m/s after 4 seconds at −2 m/s²
v₀ = v − a × t
The initial velocity is −3 − (−2 × 4) = 5 m/s. Under constant acceleration, the motion crosses zero velocity and reverses direction during this interval.
Units, assumptions, and rounding
These are one-dimensional, classical motion calculations. Use velocities along a single fixed axis in the same reference frame. Speed alone does not encode a reversal; signs supply that direction here. The calculator does not combine vectors, account for curved paths or relativity, or infer a force.
When finding acceleration, the result is the change in velocity divided by positive elapsed time. It is an average over that interval, even if the actual acceleration varied. The initial- and final-velocity modes assume that the entered acceleration remains constant. No displacement or elapsed-time solution is included.
Conversions use exact definitions: 1 km = 1,000 m, 1 international mile = 1,609.344 m, 1 international foot = 0.3048 m, 1 minute = 60 seconds, and 1 hour = 3,600 seconds. One g₀ is exactly 9.80665 m/s². This conventional standard-gravity unit is not a measurement of gravity at your location; selecting it adds no gravitational acceleration to the calculation.
Active inputs accept at most 64 characters, 15 integer digits, and 10 decimal places. Expressions, scientific notation, and units inside numeric fields are not accepted. Zero and negative velocities or accelerations are valid. Elapsed time must be greater than zero. Hidden fields are disabled and ignored.
Conversions and arithmetic retain exact fractions. Only displayed numbers are rounded, with halfway values rounded away from zero and trailing zeros omitted. ≈ identifies rounding; a very small signed number can display as ≈ 0. Changing the result unit or decimal places updates the display without creating a recent-calculation entry. More digits do not establish greater measurement accuracy.
References: OpenStax — motion with constant acceleration and NIST Guide to the SI — unit conversion factors.
Common questions
Does negative acceleration always mean slowing down?
No. A negative acceleration points in the negative direction. If the velocity is also negative, the object can gain speed. For example, starting at −2 m/s with −1 m/s² for 3 s gives −5 m/s: the speed increases from 2 to 5 m/s.
Is zero average acceleration the same as no acceleration?
No. An object may speed up and slow down yet finish with its original velocity. Its average acceleration over that full interval is zero, while its acceleration at particular times may be nonzero.
Can I use this for falling objects?
You may enter an acceleration for an ideal constant-acceleration model, with a consistent sign. The calculator does not determine local gravity, air resistance, terminal speed, impact forces, or drop distance. The g₀ unit only provides a conventional conversion factor.
Why is zero elapsed time rejected?
Average acceleration would require division by zero. This calculator uses a positive interval in every mode so its inputs consistently describe motion over time.
Why does a small negative result appear as ≈ 0?
The selected decimal places cannot show its magnitude. The calculation retains the negative, unrounded number. Increase the display precision or choose a different result unit.