VSWR, Return Loss & Reflection Coefficient Converter

Convert between VSWR, return loss, reflection coefficient and mismatch loss.

Example: 2:1 VSWR is 9.5 dB return loss — 11.1% of the power reflected, costing 0.51 dB.

Inputs

Starting from

Value

System impedance(Ω)

Result

VSWR: 2:1
Return loss: 9.54 dB
Reflection coefficient |Γ|: 0.3333
Power reflected: 11.11%
Power delivered: 88.89%
Mismatch loss: 0.512 dB
Load impedance (high): 100 Ω
Load impedance (low): 25 Ω

A 2:1 VSWR reflects 11.1% of the power, costing 0.51 dB. For perspective, 2:1 — often treated as a red line — loses only 0.51 dB, which is under 12% of the power.
Two different loads give the same VSWR: 25 Ω and 100 Ω. VSWR alone cannot tell you which, or whether the load is reactive — that needs a vector measurement, not a scalar SWR meter.

The same quantity, four ways

VSWR	Return loss	\|Γ\|	Power reflected	Mismatch loss
1.05:1	32.3 dB	0.024	0.1%	0 dB
1.2:1	20.8 dB	0.091	0.8%	0.04 dB
1.5:1	14 dB	0.2	4%	0.18 dB
2:1	9.5 dB	0.333	11.1%	0.51 dB
2.5:1	7.4 dB	0.429	18.4%	0.88 dB
3:1	6 dB	0.5	25%	1.25 dB
5:1	3.5 dB	0.667	44.4%	2.55 dB
10:1	1.7 dB	0.818	66.9%	4.81 dB

Formula

VSWR = (1 + |Γ|) / (1 − |Γ|)    RL = −20·log₁₀|Γ|

Worked example

2:1 VSWR is 9.5 dB return loss — 11.1% of the power reflected, costing 0.51 dB.

VSWR = (1 + |Γ|) / (1 − |Γ|)
(1 + 0.3333) / (1 − 0.3333)
2:1
return loss = −20·log₁₀|Γ|
−20·log₁₀(0.3333)
9.54 dB
mismatch loss = −10·log₁₀(1 − |Γ|²)
−10·log₁₀(1 − 0.1111)
0.512 dB
The power actually lost to the mismatch — usually far less than the VSWR figure suggests.

Frequently asked questions

What VSWR is acceptable?

Below 2:1 is the usual target, and that only loses 0.51 dB — about 11% of the power. The real reason to keep VSWR low is not the lost power but the stress reflected energy puts on the transmitter output stage.

What is the difference between return loss and mismatch loss?

Return loss describes how much power comes back; mismatch loss describes how much fails to get through. They are very different numbers: a 10 dB return loss means 10% reflected, which is only 0.46 dB of mismatch loss.

Why can't I work out my load impedance from VSWR alone?

Because VSWR is a scalar. Two resistive loads give the same reading — one above and one below the system impedance — and reactive loads add a whole family more. Distinguishing them needs a vector measurement, which is what a VNA and a Smith chart provide.

Does a high VSWR damage my transmitter?

It can. The reflected wave combines with the forward wave to raise voltage and current in the output stage beyond what a matched load would produce. Most modern transmitters detect this and fold back power or shut down rather than fail.

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