Enter a known RF value — VSWR, Reflection Coefficient, or Return Loss (dB) — and this VSWR Calculator converts it into all three forms at once. You also get Reflected Power (%) and Mismatch Loss (dB) so you can fully assess your transmission line's impedance match quality.
VSWR
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Reflection Coefficient (Γ)
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Return Loss
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Reflected Power
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Mismatch Loss
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Transmitted Power
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VSWR (Voltage Standing Wave Ratio) measures how well a transmission line is matched to its load. A perfect match gives a VSWR of 1.0, meaning no power is reflected. Higher VSWR values indicate more reflected power, which reduces efficiency and can damage transmitters.
The reflection coefficient (Γ) is calculated from VSWR using the formula Γ = (VSWR − 1) / (VSWR + 1). Conversely, VSWR = (1 + Γ) / (1 − Γ). The reflection coefficient ranges from 0 (perfect match) to 1 (total reflection).
Return loss is expressed in decibels and equals −20 × log₁₀(Γ). A higher return loss (more positive dB) means less reflected power and a better match. For example, a VSWR of 2.0 corresponds to a return loss of approximately 9.54 dB.
Reflected power percentage is the fraction of incident power that bounces back from the load, calculated as Γ² × 100%. A VSWR of 2.0 reflects about 11.1% of incident power, while a perfect VSWR of 1.0 reflects 0%.
Mismatch loss is the power lost due to impedance mismatch, expressed in dB. It is calculated as −10 × log₁₀(1 − Γ²). Even modest VSWR values can cause measurable mismatch loss, reducing the power delivered to your antenna or load.
For most RF applications, a VSWR of 1.5:1 or lower is considered good, corresponding to about 4% reflected power. Broadcast and high-power transmitter systems often require VSWR below 1.1:1. Consumer antennas typically specify VSWR ≤ 2.0:1.
No. VSWR is always 1.0 or greater. A value of exactly 1.0 represents a perfect impedance match with no reflected power. Values below 1.0 are physically meaningless in passive systems.
From forward power (Pf) and reflected power (Pr), the reflection coefficient is Γ = √(Pr / Pf), and then VSWR = (1 + Γ) / (1 − Γ). For example, if 10 W is transmitted and 1 W is reflected, Γ ≈ 0.316 and VSWR ≈ 1.925.