This tool uses the impedance of the source and load to calculate the impedance mismatch. It also calculates

- Reflection Coefficient
- VSWR (Voltage Standing Wave Ratio)
- Return loss
- Mismatch loss
- Forward power
- Reflected power

## Formula

**Source Impedance = Z _{0}**

**Complex Load Impedance = R + j*X**

**Absolute Load Impedance = √(R ^{2} + X^{2}**)

**Γ = √[(R-Z _{0})^{2} + X^{2}] / √[(R+Z_{0})^{2} + X^{2}]**

**Mismatch Loss (dB) = -10*Log _{10}(1 – |Γ|^{2}**)

**Return Loss (dB) = -20*Log _{10}(|Γ|**)

**Reflected Power (%) = 100*(|Γ| ^{2})**

**Transmitted Power (%) = 100*(1 – |Γ| ^{2})**

## Example Calculations

**Complex Load**

For a source impedance of 50 ohm and complex load impedance of 25 + j*25, the return loss is 7 dB and 20% of the power is reflected back with the balance of 80% transferred forward.

If the source and the load are perfectly matched, the VSWR is 1 and 100% of the power is transferred.

**50 ohm – 75 ohm mismatch loss**

A question that comes up often in the context of using an amplifier or filter designed for 75 ohm in a 50 ohm system. In this case, what’s the mismatch loss?

When you use those numbers in the calculator above for the load Impedance = R + j*X with R= 75, X = 0

The mismatch loss is calculated to be **0.18 dB**. As a result of this mismatch, only 4% of the incident power is reflected back, while 96% is transmitted forward.

**Related Calculators**

- VSWR to S11 – use this tool to find the S11 (S-parameter at port 1 of a two port network)
- Match 50 ohm to any other impedance value using this calculator (both resistive and reactive circuit options are presented)