Enter the reflected power and incident power into the calculator to determine the return loss. This calculator can also evaluate any of the variables given the others are known.

Return Loss Formula

The following formula is used to calculate the return loss.

RL = -20 * log10 (P_r / P_i)


  • RL is the return loss (dB) P_r is the reflected power (W) P_i is the incident power (W)

To calculate the return loss, divide the reflected power by the incident power. Then, take the base 10 logarithm of the quotient. Multiply the result by -20 to get the return loss in decibels.

What is a Return Loss?

Return loss is a measure of how well a device or system reflects power in a signal back to its source, often used in telecommunications. It is expressed in decibels (dB) and indicates the ratio of power arriving at a device to the power reflected back. A higher return loss value indicates a lower amount of reflection, meaning the system or device is better at transmitting power efficiently. This is desirable as it reduces signal distortion and improves overall system performance.

How to Calculate Return Loss?

The following steps outline how to calculate the Return Loss.

  1. First, determine the reflected power (Pr) in watts.
  2. Next, determine the incident power (Pi) in watts.
  3. Next, use the formula RL = -20 * log10 (Pr / Pi) to calculate the Return Loss.
  4. Finally, calculate the Return Loss in decibels (dB).
  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.

reflected power (Pr) = 0.5 W

incident power (Pi) = 2 W