Enter the total time (hrs) and the no light time (hrs) into the Calculator. The calculator will evaluate the Light Time. 

Light Time Formula

LT = TT - NT


  • LT is the Light Time (hrs)
  • TT is the total time (hrs)
  • NT is the no light time (hrs)

To calculate Light Time, subtract the no light time from the total time.

How to Calculate Light Time?

The following steps outline how to calculate Light Time.

  1. First, determine the total time (hrs). 
  2. Next, determine the no light time (hrs). 
  3. Next, gather the formula from above = LT = TT – NT.
  4. Finally, calculate the Light Time.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

total time (hrs) = 24

no light time (hrs) = 12