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SWR & Return Loss Calculator
Enter any one of SWR, return loss (dB), or reflection coefficient to calculate the other two, for antenna and RF matching work.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
SWR
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Return loss
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|Γ|
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How SWR & Return Loss Calculator works
- Pick which value you're starting from — SWR, return loss in dB, or the reflection coefficient magnitude |Γ|.
- Enter that value; the other two update immediately, along with the percentage of power being reflected.
- Use the result to judge an antenna, feedline, or matching network — lower SWR and higher return loss both mean a better match.
The formulas
All three quantities describe the same impedance mismatch:
|Γ| = (SWR − 1) / (SWR + 1) · RL(dB) = −20·log₁₀(|Γ|) · power reflected = |Γ|²
Example: SWR of 2:1 gives |Γ| = (2−1)/(2+1) = 0.333, a return loss of about 9.5 dB, and roughly 11% of forward power reflected.
FAQ
What does an SWR of 1.5:1 actually mean?
A perfect 50Ω match gives 1:1. At 1.5:1, about 4% of your forward power is reflected back toward the transmitter instead of radiating — usable for most antenna work, and well under the common 2:1 "acceptable" threshold.
Why would I use return loss instead of SWR?
Return loss (in dB) is what most vector network analyzers display directly, and it compresses better on a log scale — a return loss of 20 dB or higher (SWR under about 1.22:1) is considered an excellent match for most RF work.
Can SWR be less than 1?
No — 1:1 represents a perfect match with zero reflection, so SWR is mathematically bounded below at 1. Return loss and |Γ| are bounded too: |Γ| runs from 0 (perfect match) to 1 (total reflection, open or short circuit).
How we compare
| Feature | Online Tool Store | Calculating by hand | A VNA's built-in display |
|---|---|---|---|
| No file upload — runs in your browser | ✓ | N/A | ✗ |
| No sign-up required | ✓ | ✓ | ✗ |
| Free, no watermark | ✓ | ✓ | ✗ |
If you already have a reading from an analyzer or SWR meter and just need it converted, this is faster than re-deriving the log formula by hand — free, no install, and it works from any of the three starting values.