Calculators & Tools
Standing Wave Ratio (SWR) Calculator
Standing Wave Ratio (SWR) measures how efficiently RF power is transferred from your transmitter through the feedline to your antenna. A lower SWR indicates a better impedance match and more efficient power transfer. Higher SWR values indicate increasing reflected power, reduced efficiency, and the potential for transmitter stress if left uncorrected.
Enter forward and reflected power
W
W
Formula Reference
SWR Formula
SWR = (1 + √(Preflected / Pforward))─────────────────────────────────────────(1 − √(Preflected / Pforward))
Where √(Preflected / Pforward) is the reflection coefficient (Γ). SWR is always ≥ 1.0.
Typical SWR Guide
| SWR | Condition |
|---|---|
| 1.0 : 1 | Perfect Match |
| 1.2 : 1 | Excellent |
| 1.5 : 1 | Very Good |
| 2.0 : 1 | Acceptable |
| 3.0 : 1 | Needs Improvement |
| 5.0 : 1 | High Reflection |
| 10.0 : 1 | Severe Mismatch |
Operating Status Levels
Excellent
1.0 – 1.5 : 1Nearly perfect antenna match.
Good
1.5 – 2.0 : 1Suitable for nearly all amateur radio operation.
Fair
2.0 – 3.0 : 1Usable, but antenna tuning is recommended.
Poor
3.0 – 5.0 : 1Significant reflected power. Reduce power and investigate antenna or feedline issues.
Critical
> 5.0 : 1High risk of transmitter protection activating or equipment damage on radios without SWR protection. Correct the antenna system before transmitting.
Troubleshooting High SWR
- Incorrect antenna length
- Feedline damage
- Poor coax connectors
- Water intrusion
- Missing or defective balun
- Poor ground system
- Nearby metal objects
- Improper antenna height
- Faulty antenna tuner
- Loose mechanical connections
Practical Tips
Good Operating Practice
Always measure SWR at low transmitter power before operating at full output.
After making antenna adjustments, recheck SWR across the entire intended operating band rather than at a single frequency.