Enter the maximum voltage and the minimum voltage into the calculator to determine the voltage standing wave ratio (VSWR).

VSWR Formula

The following formula is used to calculate a voltage standing wave ratio: 

VSWR = Vmax / Vmin
  • Where VSWR is the voltage standing wave ratio
  • Vmax is the maximum voltage
  • Vmin is the minimum voltage

To calculate VSWR, divide the maximum voltage by the minimum voltage.

VSWR can also be calculated using several other formulas. One of which used the reflection coefficient as shown: 

VSWR = 1+ r / 1 - r
  • Where r is the reflection coefficient

VSWR Definition

What is VSWR?

VSWR stands for voltage standing wave ratio. It is a measure of how efficiently radio frequency power is transmitted from a source to a load through a transmission line.

Example Problem

How to calculate VSWR?

  1. First, determine the maximum voltage.

    This is the maximum voltage of the signal along the transmission line. For this example, the maximum voltage is found to be 50 V.

  2. Next, determine the minimum voltage.

    This is the minimum voltage along the same line. In this case, the minimum voltage is found to be 20V.

  3. Finally, calculate the VSWR.

    Calculate the voltage standing wave ratio using the formula above:
    VSWR = Vmax / Vmin
    VSWR = 50/20
    VSWR = 2.5