Time Dilation Calculator

Time dilation is a phenomenon predicted by Einstein's special relativity where time passes more slowly for an object moving at high speed relative to a stationary observer. The faster the object moves, the more pronounced the effect becomes. At everyday speeds, the difference is immeasurably tiny, but near the speed of light it becomes dramatic.

Time dilation is calculated using the formula Δt′ = γ × Δt, where Δt is the proper time (experienced by the moving observer), γ is the Lorentz factor (1 / √(1 − v²/c²)), and v is the velocity of the moving object. The result Δt′ is the dilated time experienced by the stationary observer — always greater than the proper time.

The Lorentz factor (γ, gamma) is a dimensionless number that quantifies how much time, length, and relativistic mass change for a moving object. At rest γ = 1, meaning no relativistic effects. As velocity approaches the speed of light, γ grows toward infinity, meaning time dilation becomes extreme.

Proper time (Δt) is the time measured by a clock travelling with the moving object — it's what the traveler actually experiences. Given dilated time Δt′ and velocity v, you can rearrange the formula: Δt = Δt′ / γ = Δt′ × √(1 − v²/c²).

Photons (particles of light) travel at exactly c, which would make the Lorentz factor infinite. In theory, a photon experiences zero proper time — from a photon's perspective, no time passes at all between emission and absorption. However, this is a limiting case and photons cannot truly be assigned a rest frame under special relativity.

The twin paradox is a famous thought experiment where one twin travels on a high-speed spaceship and returns younger than the twin who stayed on Earth. The traveling twin experiences less proper time because of time dilation. This is not actually a paradox — special relativity fully resolves it, since the traveling twin undergoes acceleration (changing reference frames), breaking the symmetry.

Yes. Time dilation has been confirmed multiple times. GPS satellites experience measurable time dilation and must be corrected for relativistic effects to maintain accuracy. Muons produced by cosmic rays in the upper atmosphere live far longer than their measured half-lives would suggest — exactly as predicted by time dilation.

Special relativistic time dilation occurs due to relative velocity — the faster you move, the slower your clock ticks relative to a stationary observer. Gravitational time dilation (from general relativity) occurs due to differences in gravitational potential — clocks closer to a massive object (stronger gravity) tick slower than those farther away. Both effects are real and measurable.