SWR Calculator

Compute SWR from forward/reflected power, return loss, or reflection coefficient. Includes derived metrics and Show Work.

How to Use

  1. Select an input mode (Power, Return Loss, or Γ).
  2. Enter the required values and units.
  3. Read SWR and derived metrics instantly.
  4. Open “Show Work” to see formulas and steps.
Match Lab View
Visual feedback: reflected power ratio + match quality.
SWR
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Return Loss
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Γ
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Reflected
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Quality: —
Forward vs Reflected Power Reflected: — Tip: For power mode, reflected % ≈ (Pref / Pfwd) × 100.
Inputs & Settings
Choose a mode and enter values. Results update instantly. Share links are generated only by button.
Power is most common when using an SWR/power meter.
Optional reference (typical: 50Ω, 75Ω). Not required to compute SWR from power/RL/Γ.
Enter measured forward power.
Must be ≤ forward power in normal measurement.
Show Work (step-by-step)
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Work uses standard RF definitions: |Γ|, return loss (dB), and power ratios.

SWR Formulas (Reference)

  • From power: |Γ| = √(Pref / Pfwd)
  • SWR from Γ: SWR = (1 + |Γ|) / (1 − |Γ|)
  • Return Loss: RL(dB) = −20·log10(|Γ|)
  • Reflected % (power): 100·|Γ|²
  • Mismatch Loss: ML(dB) = −10·log10(1 − |Γ|²)
Note: These are mismatch metrics at the measurement point; feedline loss can make shack SWR differ from antenna SWR.

FAQ

What is a “good” SWR?

Common targets: ≤1.5:1 is excellent, ≤2.0:1 is usually acceptable for many radios/antennas. Lower is better.

Why does my SWR change with frequency?

Antenna impedance varies across the band. SWR rises as you move away from resonance or the matching network’s design point.

Can coax loss “hide” a bad antenna match?

Yes. Lossy feedline can reduce reflected power at the meter, making SWR look better than the actual antenna match.

Is SWR the same as return loss?

They’re related. Return loss is a dB measure derived from |Γ|; SWR is a ratio derived from |Γ|. Both describe mismatch.

Tool Info

Last updated:

Updates may include UI improvements, additional RF metrics, and edge-case handling.