Online Tool Store
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 works right here on your device — nothing gets sent out.
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.