// S-Parameters › VSWR

VSWR / Return Loss Calculator

Convert between VSWR, Return Loss, Reflection Coefficient (Γ), Mismatch Loss, and Transmitted Power. Enter any one value and all others are calculated instantly.

// Input — enter any one value

VSWR

Return Loss

Reflection Coefficient |Γ|

linear

Reflection Coefficient |Γ|

Impedance ZL (with Z₀ = 50 Ω)

// Results

📡

Enter any value on the left to calculate all others

VSWR—:1

Return Loss—dB

Reflection Coeff |Γ|—linear

Reflection Coeff |Γ|—dB

Mismatch Loss—dB

Transmitted Power—%

Reflected Power—%

ZL (at Z₀ = 50 Ω)—Ω

MATCH QUALITY

Perfect (1.0)—Open/Short (∞)

Key relationships
Γ = (ZL−Z₀)/(ZL+Z₀)
VSWR = (1+|Γ|)/(1−|Γ|)
RL = −20·log₁₀(|Γ|) [dB]
Mismatch Loss = −10·log₁₀(1−|Γ|²) [dB]

About VSWR and Return Loss

When an RF signal travels along a transmission line and encounters an impedance mismatch â€” a connector, an amplifier input, or an antenna â€” some of the power reflects back toward the source. VSWR (Voltage Standing Wave Ratio) and return loss are two ways of expressing the severity of this mismatch.

VSWR Explained

VSWR is the ratio of the maximum to minimum voltage along the transmission line, created by the superposition of the forward and reflected waves. A perfect match gives VSWR = 1.0 (no reflection). An open or short circuit gives VSWR = infinity (total reflection). Most RF specifications require VSWR below 2:1, which corresponds to a return loss of approximately 9.5 dB and means less than 11% of power is reflected.

Return Loss vs VSWR

Return loss is the same information expressed in dB: RL = -20*log10(|Gamma|). A return loss of 20 dB means only 1% of power is reflected â€” a very good match. Return loss is preferred by RF engineers because it scales more intuitively with power at high frequencies. VSWR is preferred in antenna specifications and broadcast engineering.

Mismatch Loss

Mismatch loss is the power lost due to reflection: ML = -10*log10(1 - |Gamma|^2) dB. For a VSWR of 1.5 (return loss 14 dB), the mismatch loss is only 0.18 dB â€” often negligible. But at VSWR = 3 (return loss 6 dB), mismatch loss reaches 1.25 dB â€” significant in a low-noise receiver front-end.