What acceleration means
Acceleration is how quickly velocity changes. If a car's speed climbs from 0 to 27.8 m/s (100 km/h) over 8 seconds, its speed goes up by an average of 3.47 m/s every second. Slowing down is acceleration too, just with a negative sign.
The calculator uses the standard symbols from physics class: u for initial velocity, v for final velocity, t for time, a for acceleration and s for distance (displacement).
The formula
v = u + a·t
u = v − a·t
t = (v − u) ÷ a
s = u·t + ½·a·t²
acceleration in g = a ÷ 9.80665
All five come from the same idea and assume the acceleration stays constant. Velocities are converted to m/s first: divide km/h by 3.6, or multiply mph by 0.44704. Standard gravity, g, is 9.80665 m/s².
Example: 0 to 100 km/h in 8 seconds
A car accelerates from a standstill to 100 km/h in 8 seconds (the default values).
| Step | Result |
|---|---|
| Final velocity in m/s: 100 ÷ 3.6 | 27.78 m/s |
| a = (27.78 − 0) ÷ 8 | 3.472 m/s² |
| In g's: 3.472 ÷ 9.80665 | 0.3541 g |
| Distance: 0 × 8 + ½ × 3.472 × 8² | 111.1 m (364.5 ft) |
Typical accelerations
| Situation | Approximate acceleration |
|---|---|
| Family car, 0–100 km/h in 10 s | 2.8 m/s² (0.28 g) |
| Free fall near Earth (no air resistance) | 9.81 m/s² (1 g) |
| Hard braking on dry pavement | about 7–9 m/s² (0.7–0.9 g) |
Common mistakes
- Not converting km/h or mph. 100 ÷ 8 = 12.5 is not the acceleration in m/s²; convert 100 km/h to 27.78 m/s first.
- Mixing up u and v. Final minus initial. Swapping them flips the sign.
- Using average speed as final speed. A car that ends at 100 km/h averaged only 50 km/h along the way if it accelerated evenly from rest.
- Assuming constant acceleration when it isn't. Real cars pull hardest in low gears, so these formulas give an average.
Frequently asked questions
What is the formula for acceleration?
Acceleration is the change in velocity divided by the time it takes: a = (v − u) ÷ t, where u is the starting velocity, v the final velocity and t the time. In SI units the answer is in meters per second squared (m/s²).
What does m/s² mean?
Meters per second, per second. An acceleration of 3 m/s² means the speed goes up by 3 m/s every second. After 1 second you're at 3 m/s, after 2 seconds 6 m/s, and so on.
What is the acceleration of a car going 0 to 60 mph in 8 seconds?
60 mph is 26.82 m/s, so the average acceleration is 26.82 ÷ 8 = 3.35 m/s², or about 0.34 g. A 0 to 100 km/h time of 8 seconds works out to 3.47 m/s².
What does 1 g of acceleration mean?
1 g is the acceleration of a freely falling object near Earth's surface, standard gravity, defined as exactly 9.80665 m/s². Dividing any acceleration by 9.80665 gives it in g's. Most cars accelerate at well under 1 g; fast roller coasters and fighter jets reach several g.
Can acceleration be negative?
Yes. Negative acceleration (often called deceleration) means the velocity is decreasing in the direction you've called positive. Braking from 30 m/s to 0 in 5 seconds is an acceleration of −6 m/s².
How do I find the distance traveled while accelerating?
Use s = ut + ½at², or the equivalent s = (u + v) ÷ 2 × t. Both assume the acceleration is constant. For 0 to 100 km/h in 8 seconds, the car covers about 111 meters.
Rates and figures last checked October 2026.
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