Use this tool to calculate the Return Loss (RL) from S11.
Return Loss is a measure of mismatch at a transition in an RF circuit.
- S11 – either linear or dB value can be used
S11 is the input reflection coefficient  with a value between 0 and 1. (Entering values outside this range will result in meaningless output). Referring to the picture of a two port network shown below, S11 = b1/a1 (when a2=0)
If a1, b1 and S11 are all linear numbers,
Return Loss = 10*Log10(a1/b1)
RL = -10*Log10(S11)
On the other hand, if S11 is expressed in dB
RL = -S11dB
Return Loss is always a positive number as a1 > b1
If the reflected signal b1 = 0, then all of the input signal a1 is transmitted forward and the return loss RL = ∞.
If all of the input signal is reflected back, then b1=a1 and none of it is transmitted forward. This is the poorest match possible and RL = 0.
If S11 = 0.1, the Return Loss is calculated to be 20 dB.
- S11 to Voltage Standing Wave Ratio
- S11 to Impedance
- S11 to Reflection Coefficient
- S11 Linear to dB
- S11 to Reflected Power
 Scattering Parameters on Wikipedia