What is acceleration?
Acceleration is the rate at which an object's velocity changes over time. In the simplest kinematic equation it is defined as a = (v − v₀) / t, where v is the final velocity, v₀ is the initial velocity, and t is the elapsed time. The SI unit is metres per second squared (m/s²). A positive value means the object is speeding up; a negative value (deceleration) means it is slowing down. Earth's gravitational acceleration is approximately 9.81 m/s², often denoted as 1 g.
How to use this calculator
Choose what you want to find—Acceleration, Final Velocity, Initial Velocity, or Time—with the toggle buttons. Enter the remaining known values and click Calculate. The result card shows the answer, the applied formula, a plain-language interpretation, and (when solving for acceleration) conversions to km/h/s, ft/s², g, and Gal.
Rearranging the formula
From the base equation you can derive three rearrangements: v = v₀ + a·t (find final velocity), v₀ = v − a·t (find initial velocity), and t = (v − v₀) / a (find time). The calculator handles the algebra automatically—just select the unknown and enter the other values.
Practical applications
Automotive engineers measure 0-to-100 km/h times and convert them to average acceleration. Aerospace designers calculate launch g-forces to protect astronauts and payloads. Athletes and coaches analyse sprint acceleration to optimise performance. Physicists model free-fall, projectile motion, and orbital mechanics using acceleration as a key variable. Even everyday braking distances depend directly on deceleration.
Tips
Always use consistent SI units (m/s for velocity, seconds for time). Negative acceleration simply means the object is slowing down—it is not an error. For free-fall problems use a = 9.81 m/s² (or −9.81 if upward is positive). This free tool runs entirely in your browser with no sign-up, no download, and instant results on any device. Bookmark it for quick acceleration calculations whenever you need them.