Modern GPS systems must account for two relativistic effects each day: special relativity causes the high-speed satellite clocks to run slower, while general relativity makes the clocks in a weaker gravitational field run faster. Together, these effects create a daily time difference of about 38 microseconds, which would cause GPS positions to drift by roughly 10 kilometers per day. Precise relativistic time corrections are therefore essential to maintain accurate positioning on our devices.
Horizontal: speed as a percentage of light speed v/c.
Vertical: time dilation factor γ (larger means time runs slower).
Use either input: enter speed as a percentage of light speed, or enter the time dilation factor you want; the two fields stay in sync.
Example: 99 means 99% of light speed. If you type more than two digits, it will auto-convert to one decimal place (e.g. 999 → 99.9).
Example: 365 means when you experience 1 second, the outside world experiences 365 seconds.
This time dilation calculator is based on the Lorentz factor from special relativity, γ = 1 / √(1 − v²/c²). It shows how much slower time runs in a moving frame, relative to a stationary observer, as the speed v approaches the speed of light. Enter a speed as a percentage of light speed, or enter a time dilation factor γ directly, to compare how time passes at different speeds.
It is useful for learning relativity, for physics education, and for quick special-relativity calculations. Modern GPS satellites are subject to both special and general relativistic effects, which together add up to roughly 38 microseconds per day — enough to drift positions by about 10 kilometers a day without relativistic correction.