Standing Wave Ratio (SWR) is a measure of how well your antenna system is matched to your transmission line. A low SWR indicates efficient power transfer; a high SWR suggests reflected energy and potential loss or equipment stress.

This calculator uses forward and reflected power to compute SWR: $$\text{SWR}=\frac{1+\sqrt{P_{\text{reflected}}/P_{\text{forward}}}}{1-\sqrt{P_{\text{reflected}}/P_{\text{forward}}}}$$

Enter your measured forward and reflected power in watts. The result will show the SWR — ideally as close to 1.0 as possible.

A perfectly matched system has an SWR of 1.0. An SWR below 2.0 is generally acceptable for most ham operations. High SWR can cause heat buildup, inefficiency, or even damage to some transmitters without protection circuitry.