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Return Loss Calculator

Work out return loss instantly with clear inputs, formula shown and shareable results.

About Return Loss Calculator

Return loss is the reflected power expressed in decibels below the incident power: rho = 10^(-RL/20). Higher return loss means a better match — 20 dB corresponds to 1% reflected power and an SWR of 1.22:1, while 10 dB is 10% reflected and 1.92:1.

Formula

Return loss

rho = 10^(-RL/20); VSWR = (1 + rho)/(1 - rho); Preflected = Pfwd x rho^2

Worked example

With the default values below, Return Loss Calculator returns VSWR of 1.50. Change any input above and every figure here is recalculated in your browser.

Inputs used

Return loss
14 dB
Forward power
50 W

Results

VSWR
1.50 :1
Reflection coefficient
0.19953
Reflected power
1.99 W
Power delivered to the load
48.01 W

Step by step

  1. 1Values used
  2. 2Return loss
  3. 3VSWR= 1.50 :1
  4. 4Reflection coefficient= 0.19953
  5. 5Reflected power= 1.99 W
  6. 6Power delivered to the load= 48.01 W

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 5 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is return loss positive or negative?

By convention it is quoted as a positive number of decibels of loss. Network analysers display S11 as a negative dB figure, which is the same information.

What return loss is good enough?

10 dB (1.9:1) is usually acceptable, 15 dB (1.4:1) is good and 20 dB (1.2:1) is excellent for most antenna and filter work.

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