Enter the power transmitted to the load before and after insertion into the calculator to determine the insertion loss (dB).

Insertion Loss Formula

The following formula is used to calculate the insertion loss of a transmission line.

IL = 10*log( Pt/Pr) 
  • Where IL is the insertion loss (dB)
  • Pt is the power before insertion
  • Pr is the power after insertion

To calculate an insertion loss, take the log of the ratio of power before the insertion over the power after insertion, then multiply by 10.

Alternatively, insertion loss can also be explored with electronic filters using the following formula:

IL = 20*log(V1/V2)
  • Where V1 is the signal without a filter installed
  • V2 is the signal with a filter installed

The calculator will evaluate both values.

Insertion Loss Definition

Insertion loss is most commonly defined as the loss of signal power resulting from the insertion of a device in a transmission line.

Example Problem

How to calculate insertion loss?

First, determine the power transmitted before insertion of the device. For this example problem, the power before insertion is found to be 10 W.

Next, determine the power transmitted after a device is inserted in the transmission line. In this case, the power after is found to be 5 W.

Finally, calculate the insertional loss using the formula above:

= 10*log10( Pt/Pr)

= 10*log10( 10/5)

= 3.0102 dB