Enter the total time interval and the velocity of the observer to calculate the relative time seen by that observer. This time dilation calculator can also be considered a relative time calculator.

Time Dilation Formula

The following equation can be used to calculate the relative time seen by an observer traveling at fast speeds.

RT = t * √(1 – v²/c²)

  • Where RT is the relative time (seconds)
  • t is the actual time (seconds)
  • v is the velocity of the observer
  • c is the speed of light. (299792458 m/s)

To calculate the relative time dilation, divide the velocity squared by the speed of light squared, subtract this result from one, then take the square root. Finally, multiply the actual time by the previous result.

As with most things involving relativity, the speed of light is present in this equation. For any time to be noticeably different, the observer must be traveling at extremely fast speeds. If you play around with the values in the calculator you can see this effect. Digging a little deeper into this formula, you may notice that this takes a square root of a value. What if this value is less than 0 or negative? Well, it cant be. That’s because the denominator for the equation is the speed of light, and nothing can travel faster than the speed of light. As the observer velocity approaches the speed of light, the relative time will approach 0.

Time Dilation Definition

Time dilation is defined as the change in time of a traveler relative to an observer as they approach the speed of light.

How to calculate time dilation?

How to calculate time dilation?

  1. First, determine the time of the observer.

    Measure the time recorded by the observer.

  2. Next, determine the speed of the observer.

    This is the speed the observer is travelling at.

  3. Finally, calculate the time dilation.

    Calculate the time dilation using the equation.


What is time dilation?

Time dilation is the phenomena of time slowing down when an object approaches the speed of light.