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.

Enter

**S11**– either linear or dB value can be used

**Background**

**S11** is the input reflection coefficient [1] 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)

**Formula**

If a1, b1 and S11 are all linear numbers,

**Return Loss = 10*Log _{10}(a1/b1)**

or

**RL = -10*Log _{10}(S11)**

On the other hand, if S11 is expressed in dB

**RL = -S11 _{dB}**

**Return Loss is always a positive number as a1 > b1**

**Example Calculations**

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**.

**Related Calculators**

- S11 to Voltage Standing Wave Ratio
- S11 to Impedance
- S11 to Reflection Coefficient
- S11 Linear to dB
- S11 to Reflected Power

**References**

[1] Scattering Parameters on Wikipedia