VSWR Calculator

Here's a simple VSWR calculator. Enter a value for VSWR (remember: VSWR should be a number larger than 1.0 or the results don't mean anything!).

Enter VSWR: Calculate!

Reflection Coefficient

Reflected Power (%)

Reflected Power (dB)

Mismatch Loss (dB)

Where do these calculations come from? Well, start with the formula for VSWR:

If we invert this formula, we can calculate the reflection coefficient (, or the return loss, s11) from the VSWR:

Now, this reflection coefficient is actually defined in terms of voltage. We really want to know how much power is being reflected. This will be proportional to the square of the voltage (V^2). Hence, the reflected power in percent will be:

We can convert reflected power to decibels simply:

Finally, the power is either reflected or delivered to the antenna. The amount delivered to the antenna is written as (), and is simply (1-^2). This is known as mismatch loss. This is the amount of power that is lost due to impedance mismatch, and we can calculate that fairly easily:

And that's all we need to know to go back and forth between VSWR, s11/return loss, and mismatch loss. I hope you've had as great of a time as I've had.