Acceleration Calculator

Find acceleration from a change in speed, distance and time, speeds and distance, or net force and mass. Compare m/s², ft/s² and g for vehicle times, braking, motion problems and ideal free fall.

Bhuvan PoudelUpdated
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Time unit

Use nonnegative speeds along one straight direction. Force is signed net force; a negative force gives negative acceleration.

Your accelerationAcceleration
5.5556 m/s²
Feet per second squared
18.2269 ft/s²
Standard gravity
0.5665 g
Distance at constant acceleration
69.4444 m
Working in SI
a = (27.77777778 − 0) m/s ÷ 5 s = 5.5556 m/s²

Results use up to 4 decimal places. Exact unit factors are used internally. Motion formulas assume constant acceleration without reversal; speed-change mode gives average acceleration. Standard gravity is exactly 9.80665 m/s². Free fall assumes no air resistance.

How it works

a = (v − u) ÷ t; a = 2(s − u × t) ÷ t²; a = (v² − u²) ÷ (2s); a = F ÷ m. All quantities are converted to SI first.

  • Choose the quantities you know.
  • Enter measurements and their units.
  • Read acceleration in m/s², ft/s² and g.
  • Check the SI working and derived quantity.

Worked example: 0 to 100 km/h in 5 s: 100 km/h = 250/9 m/s. Acceleration = (250/9 − 0) ÷ 5 = 50/9 m/s², about 5.5556 m/s² or 0.5665 g.

Things to consider

  • Use elapsed time, not a timestamp.
  • Braking produces a negative result.
  • Use net force, not one of several forces.
  • Keep motion in one straight direction.
  • Vehicle times give average acceleration.

Frequently asked questions

What is the acceleration formula?

Average acceleration is change in velocity divided by elapsed time: a = (v − u) ÷ t. With constant acceleration, use a = 2(s − u × t) ÷ t² or a = (v² − u²) ÷ (2s). Here u is initial speed, v is final speed and s is distance along one direction without reversal.

What units measure acceleration?

The SI unit is metres per second squared, m/s². An acceleration of 1 m/s² changes velocity by 1 m/s each second. One m/s² is about 3.2808 ft/s².

What does 1 g mean?

One g is standard gravity, exactly 9.80665 m/s². Actual local gravity varies slightly. Ideal free fall near the surface is approximately 1 g downward without air resistance. This acceleration ratio is not a direct measurement of the force a person feels.

Is negative acceleration deceleration?

For positive speeds in one direction, a negative acceleration means the object slows down, so it is labelled deceleration here. In general physics, the sign indicates direction; negative acceleration can increase speed if velocity is also negative. This calculator's motion modes do not model that situation or reversals.

How do I convert a 0 to 100 km/h time to g?

Divide 100 by 3.6 to obtain m/s, divide by the elapsed seconds, then divide by 9.80665. At 5 seconds, the average is 5.5556 m/s² or 0.5665 g. The quick pick starts at 5 seconds; change the time for another vehicle.

How are acceleration and velocity different?

Velocity describes speed and direction. Acceleration is the rate of change of velocity. Constant speed in a straight line gives zero acceleration; turning can cause acceleration even at constant speed. These motion formulas cover straight-line motion only.

How does Newton's second law calculate acceleration?

For constant mass, net force equals mass times acceleration: F = m × a, so a = F ÷ m. Use newtons and kilograms in SI. Pound-force and pounds of mass are converted exactly; 1 lbf acting on 1 lb gives 1 g, not 1 ft/s².

Results are estimates for general information only, not financial, medical or professional advice.