How to use this calculator
Choose the unit used by your speed measurements. Enter the initial speed, final speed and elapsed seconds between them. Read the signed average acceleration in m/s² or g. The two speed-change results express the same average in familiar road-speed units per second. A speed decrease is supported without entering negative speeds.
This summarizes a measured or assumed interval; it does not predict 0–60 time from power or vehicle weight. Acceleration can vary throughout that interval. The result is not peak acceleration, a traction limit, an accelerometer reading, stopping distance or a safety rating. It excludes changes in direction, including cornering or reversing. Do not gather measurements while operating a vehicle in a way that distracts from driving.
The formula
A worked example
A hypothetical 0–60 mph interval taking 6 seconds changes speed by 60 × 0.44704 = 26.8224 m/s. Average acceleration = 26.8224 ÷ 6 = 4.4704 m/s², about 0.456 g. It is also 10 mph gained per second on average. Separately, slowing from 72 to 36 km/h in 2 seconds gives (10 − 20) ÷ 2 = −5 m/s². The minus sign describes a decrease along the chosen positive direction.
Same speed change, different elapsed time
Original hypothetical 0–60 mph intervals. These are arithmetic examples, not vehicle test results.
| Elapsed time (s) | Average (m/s²) | Average (g) | Average (mph/s) |
|---|---|---|---|
| 4 | 6.7056 | 0.684 | 15 |
| 6 | 4.4704 | 0.456 | 10 |
| 8 | 3.3528 | 0.342 | 7.5 |
Common questions
Does 0–60 in 6 seconds mean a constant 0.456 g?
No. That is the interval average. A vehicle could accelerate harder at some speeds and less at others, with the same total speed change and elapsed time. These two endpoints cannot identify the peak or the acceleration curve.
Is 0–100 km/h the same as 0–60 mph?
No. 60 mph is 96.56064 km/h. At an identical hypothetical 6 seconds, 0–100 km/h averages about 4.630 m/s², while 0–60 mph averages 4.4704 m/s². Use the actual endpoints when comparing results.
Can I calculate passing acceleration?
Yes. For example, 40–60 mph in 4 seconds averages 5 mph/s, or 2.2352 m/s². Enter both endpoints instead of treating the final speed as the whole speed change.
Why does braking give a negative result?
The final speed is lower, so final minus initial is negative for motion in the same positive direction. A result of −5 m/s² corresponds to a deceleration magnitude of 5 m/s². This sign convention does not cover reversing direction.
What if both speeds are the same?
The average along the chosen line is zero. It does not establish that speed stayed constant between the two measurements: acceleration and deceleration may have canceled over the interval.
Can this determine how far the vehicle traveled?
No. Two endpoint speeds and elapsed time do not uniquely specify distance when acceleration varies. A distance calculation using the mean of the endpoint speeds needs an additional constant-acceleration assumption, which this tool does not make.
How should I compare two timed runs?
Use the same initial and final speeds, units and timing boundaries. A timer that starts after the vehicle is already moving describes a different interval from one starting at rest. Changing those boundaries can change the result even for the same run.
Does the g result include gravity or road slope?
It is simply the calculated speed-change rate divided by standard gravity. It does not combine vertical gravity with other axes or reproduce a phone sensor’s reading. No gradient, aerodynamic drag or tire-force model is used.
Sources & calculation method
OpenStax University Physics: Average and Instantaneous Acceleration defines average acceleration as velocity change divided by elapsed time and distinguishes it from instantaneous acceleration. This tool applies that definition to straight-line vehicle motion without reversal. Examples are original calculations, not road tests.
Compare the energy change between speeds with the Vehicle Kinetic Energy Calculator. For a separate reaction-time and constant-deceleration model, use the Stopping Distance Calculator. The Power-to-Weight Ratio Calculator compares power and mass but does not predict this acceleration result.
Reference accessed September 29, 2026. The source does not endorse the site or independently review this calculator.
Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.