VSWR Calculator

Γ · RL · mismatch
:1
Reflection Γ
0.35484
Return loss
9.0
dB
Reflected
12.59
%
Through
87.41
%
Mismatch loss
0.58
dB
preset:
Γ 0.354 · 12.59% · 9dB
Narendra Kumar
Created by
Narendra Kumar
 Bahadur Merawat
Verified by
Bahadur Merawat
Last Updated: 22-02-2026

VSWR Calculator – Formula, Full Form, VSWR vs Return Loss (Complete Guide)

What is VSWR?

VSWR (Voltage Standing Wave Ratio) is an RF measurement that indicates how efficiently power is transmitted from a transmitter through a transmission line to an antenna. It quantifies the amount of signal reflected back due to impedance mismatch. A perfect system has a VSWR of 1:1, meaning no reflected power, while higher VSWR values indicate greater reflection and reduced transmission efficiency.

For example, a VSWR of 1.4 reflects about 2.8% of the forward power, while a VSWR of 4 reflects approximately 64% and VSWR of 5 reflect about to 55%.

VSWR calculation infographic showing forward and reflected power

VSWR Formula

$$\text{VSWR} = \frac{V_{\text{max}}}{V_{\text{min}}}$$

Vmax: Max voltage | Vmin: Min voltage

🔁 VSWR from Reflection Coefficient

Often in RF planning, VSWR is calculated using reflection coefficient (Γ):

$$\text{VSWR} = \frac{1 + |\Gamma|}{1 - |\Gamma|}$$

Where:

$$\Gamma = \frac{Z_L - Z_0}{Z_L + Z_0}$$

  • ZL = Load impedance
  • Z0 = Line impedance (usually 50Ω)

VSWR can be computed using three common methods:

Method 1: Vmax / Vmin

$$VSWR=\frac{V_{\text{max}}}{V_{\text{min}}}$$

Example: 5 / 2 = 2.5

Method 2: Return Loss

$$|\Gamma|=10^{-\frac{RL}{20}}$$
$$VSWR=\frac{1+|\Gamma|}{1-|\Gamma|}$$

Method 3: Reflected Power

$$|\Gamma|=\sqrt{\frac{P_r}{P_f}}$$

Then apply the VSWR formula.


What is a Good VSWR?

In real RF networks:

  • ≤ 1.3 — Excellent
  • 1.3 – 1.5 — Good (typical telecom acceptance)
  • 1.5 – 2.0 — Acceptable
  • > 2.0 — Needs attention
  • > 3.0 — Problematic

In cellular networks, 1.5:1 is commonly used as the acceptance limit.

VSWR vs Return Loss

VSWR and Return Loss both indicate impedance matching quality in RF systems. They are mathematically related but used in different practical scenarios.

Parameter VSWRReturn Loss
MeaningVoltage standing wave ratio Reflected power loss
UnitRatio (e.g., 1.5:1)dB
Ideal value1:1∞ dB
Better whenLowerHigher
Common usersField engineersRF designers

💡 Quick tip: A VSWR of 1.5:1 corresponds roughly to a Return Loss of about 14 dB.

Causes of High VSWR

  • Impedance mismatch
  • Damaged feeder cable
  • Water ingress in connector
  • Loose connectors
  • Poor antenna tuning
  • Cable bending beyond limit

How to Reduce VSWR

  • Use proper 50-ohm components
  • Avoid sharp cable bends
  • Ensure connector tightness
  • Weatherproof outdoor joints
  • Use high-quality feeders
  • Perform antenna tuning
  • Check with Site Master / VSWR meter

FAQ on VSWR

1. What is VSWR full form?

VSWR stands for Voltage Standing Wave Ratio.

2. What is a good VSWR value?

A VSWR of 1:1 is ideal. In telecom systems, values up to 1.5:1 are generally acceptable.

3. How is VSWR related to return loss?

VSWR and return loss are mathematically related through the reflection coefficient. Higher return loss means lower VSWR.

4. What causes high VSWR?

Common causes include impedance mismatch, damaged cables, loose connectors, and water ingress.

5. Why is low VSWR important?

Low VSWR ensures maximum power transfer, protects transmitters, and improves network performance.