Time Dilation Calculator
Calculate how time slows at velocities approaching the speed of light.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the Time Dilation Calculator
Enter the proper time (time measured in the rest frame) and the velocity of the moving object. The calculator computes the dilated time as observed from a stationary frame.
- Enter proper time. This is the time interval measured by a clock traveling with the object.
- Enter velocity. Provide it in m/s or as a percentage of c.
- Read the result. The dilated time and Lorentz factor appear instantly.
About the Time Dilation Calculator
Time dilation is a prediction of Einstein's special relativity: a moving clock ticks slower than a stationary one. The effect becomes significant only at velocities approaching the speed of light. At 87% of c, time passes at half the rate. GPS satellites must account for both special and general relativistic time dilation to maintain accuracy. The formula is t' = t / sqrt(1 - v2/c2), where t is the proper time, v is velocity, and c is the speed of light.
Frequently Asked Questions
What is time dilation?
Time dilation is the difference in elapsed time between two clocks due to relative velocity. A clock moving at high speed relative to an observer ticks slower from that observer's perspective.
At what speed does time dilation become noticeable?
Time dilation exists at all speeds but is negligible at everyday velocities. It becomes measurable above about 10% of c (30,000 km/s) and dramatic above 90% of c.
Has time dilation been proven?
Yes. Experiments with atomic clocks on jets, particle accelerators, and GPS satellites all confirm time dilation exactly as predicted by special relativity.