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SWR to Reflected Power Calculator

Enter the SWR your meter shows and see what share of the power is reflected, what share is delivered, and the return loss in dB. The reading assumes an ideal line with no cable loss.

Power reflected

4 %

Reflection coefficient 0.2 · 96 % delivered · return loss 13.98 dB

Ideal arithmetic for a lossless line. It is not a diagnosis and does not say whether a transmitter is safe to run.

How it works

  1. Enter the SWR reading (1 or more; 1 is a perfect match).
  2. Read the reflection coefficient and the percentage of power reflected.
  3. Check the percentage delivered and the return loss in dB.
  4. Copy the figures into your station notes.

What people use it for

  • Tuning an antenna

    See how much a 1.5:1 or a 3:1 reading really costs, before you decide whether to retune.

  • Understanding a meter

    Compare SWR, return loss and percent reflected on a single page.

  • Teaching and clubs

    Show new operators what an SWR figure means for the power.

Questions

What are the formulas?
Reflection coefficient Γ = (SWR − 1) ÷ (SWR + 1). Reflected power = 100 × Γ² in percent. Return loss = −20 × log10(Γ) dB. An SWR of 3 gives Γ = 0.5 and 25 % of the power reflected.
Is 1.5:1 bad?
It reflects 4 % of the power at the point where you measure it, so 96 % goes on. What is acceptable depends on your equipment, not on this page.
Does it say if my station is safe or working?
No. It is the ideal arithmetic for a lossless line. Cable loss changes what the meter sees, and it cannot diagnose a fault or tell you whether a transmitter is safe to run.
Why does the return loss become infinite?
At an SWR of 1 nothing is reflected (Γ = 0), and the logarithm of 0 is not finite. The page shows it as infinite.