Time Dilation Calculator
Calculate how much time slows down for a fast-moving observer using Einstein’s special relativity time dilation formula.
What time dilation means
Special relativity shows that time passes more slowly for an object moving quickly relative to an observer. This is described by t = γ × t0, where t0 is the proper time (measured by a clock moving with the object), t is the time measured by a stationary observer, and γ = 1 / √(1 – v²/c²) is the Lorentz factor.
How this calculator works
Enter the object’s velocity as a fraction of the speed of light (for example, 0.5 means half the speed of light) and the proper time interval measured on the moving object’s own clock. The calculator computes the Lorentz factor and multiplies it by the proper time to find how much time actually passes for a stationary outside observer.
At everyday speeds the Lorentz factor is extremely close to 1, so time dilation is imperceptible — it only becomes significant as velocity approaches the speed of light. This calculator is for general physics education purposes.