Enter the luminosity (watts) and the distance (m) into the Brightness Ratio Calculator. The calculator will evaluate and display the Brightness Ratio. 

Brightness Ratio Formula

The following formula is used to calculate the Brightness Ratio. 

BRR = L / (4*pi*d^2)
  • Where BRR is the Brightness Ratio (watts/m^2)
  • L is the luminosity (watts) 
  • d is the distance (m) 

To calculate the brightness ratio, divide the luminosity by the 4 times pi times the distance squared.

How to Calculate Brightness Ratio?

The following example problems outline how to calculate Brightness Ratio.

Example Problem #1:

  1. First, determine the luminosity (watts).
    • The luminosity (watts) is given as: 500.
  2. Next, determine the distance (m).
    • The distance (m) is provided as: 5.
  3. Finally, calculate the Brightness Ratio using the equation above: 

BRR = L / (4*pi*d^2)

The values given above are inserted into the equation below and the solution is calculated:

BRR = 500 / (4*3.14159*5^2) = 1.591 (watts/m^2)

Example Problem #2: 

For this problem, the variables required are provided below:

luminosity (watts) = 600

distance (m) = 10

Test your knowledge using the equation and check your answer with the calculator above.

BRR = L / (4*pi*d^2) = ?