VSWR ↔ return loss

Translate a passive impedance mismatch into reflection, return loss and reflected power.

VSWR
2:1
Return loss
9.54 dB
Reflection magnitude |Γ|
0.3333
Reflected power
11.11%
Mismatch loss
0.512 dB

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Calculation reference

|Γ| = (VSWR − 1)/(VSWR + 1); RL = −20 log₁₀|Γ|; VSWR = (1 + 10^(−RL/20))/(1 − 10^(−RL/20)).

Variables and units

VSWR is a dimensionless ratio; Γ is the voltage reflection coefficient; RL is positive return loss in dB. Reflected power = 100|Γ|²%; mismatch loss = −10 log₁₀(1 − |Γ|²) dB.

Worked example

VSWR 2:1 gives |Γ| = 1/3, return loss 9.542 dB, reflected power 11.11% and mismatch loss 0.512 dB.

Assumptions and limitations

Assumes a passive load and real positive reference impedance. VSWR 1 is a perfect match with infinite return loss. Return loss 0 dB is total reflection with infinite VSWR. Return loss is not cable insertion loss; this scalar conversion does not recover impedance phase.

Reference: Keysight reflection measurements. Cite this calculator using its permanent page URL and your access date.

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