Calculators / 02
VSWR, Return Loss and Reflection Coefficient Calculator
Return loss, the reflection coefficient and VSWR are three ways of stating one number — how much of an incident wave comes back. Start from whichever you have. One thing none of them can tell you is whether the load is above or below Z0, so unless you start from the load itself the calculator shows both loads that fit.
Reading the numbers
- A higher return loss is a better match. 20 dB means |Γ| = 0.1: a tenth of the voltage, and 1% of the power, comes back.
- Mismatch loss is the power the reflection keeps from the load. It stays small long after the reflection itself matters for signal integrity: the echo corrupts later bits even when the lost power is negligible.
- Starting from a load gives Γ its sign. Positive means the load is above Z0 and the reflection has the same polarity as the incident step.
Every value is in the address bar as you change it, so a link reproduces the calculation exactly.
Type values with SI prefixes — 100n, 2.2p, 16G — or
drag the sliders; a bare number keeps the prefix already shown.
The formulas
Go deeper — assumptions, how it is checked, and sources
Assumptions. A resistive load on a lossless line. For a complex load |Γ|, return loss and VSWR are unchanged, but the load is then any point on a circle of the Smith chart, not one of two resistances.
How it is checked. A matched load reflects nothing (infinite return loss, VSWR 1); an open or a short reflects everything (0 dB, infinite VSWR, Γ = +1 or −1); every conversion round-trips; both candidate loads reproduce the same |Γ|; and reflected plus transmitted power is 1.
Source. D. M. Pozar, Microwave Engineering, 4th ed., Wiley, 2012, §2.3.