VSWR & return loss calculator
Calculate voltage standing wave ratio, return loss, and reflection coefficient for RF impedance matching.
Standard Z₀: 50 Ω
Matching efficiency analysis
Calculation parameters
Select your input mode and enter the known values for analysis
Technical formulas
Calculation history
Standard VSWR registry
| VSWR ratio | Return loss | Reflection γ | Reflected % | System quality |
|---|---|---|---|---|
| 1.0:1 | ∞ | 0.0000 | 0.00% | Perfect (Theoretical) |
| 1.1:1 | 26.44 dB | 0.0476 | 0.23% | Excellent |
| 1.2:1 | 20.83 dB | 0.0909 | 0.83% | Excellent |
| 1.3:1 | 17.69 dB | 0.1304 | 1.70% | Excellent |
| 1.5:1 | 13.98 dB | 0.2000 | 4.00% | Excellent |
| 1.8:1 | 10.88 dB | 0.2857 | 8.16% | Good |
| 2.0:1 | 9.54 dB | 0.3333 | 11.11% | Good |
| 2.5:1 | 7.36 dB | 0.4286 | 18.37% | Acceptable |
| 3.0:1 | 6.02 dB | 0.5000 | 25.00% | Poor |
| 4.0:1 | 4.44 dB | 0.6000 | 36.00% | Poor |
| 5.0:1 | 3.52 dB | 0.6667 | 44.44% | Poor |
Understanding VSWR
What is VSWR?
VSWR (Voltage Standing Wave Ratio) is a critical metric in RF engineering that measures impedance matching between a transmitter (source) and its load (typically an antenna). It quantifies the ratio of maximum to minimum voltage in a standing wave pattern.
Why it matters
High VSWR indicates poor impedance matching and efficiency loss.
Reflection causes power to bounce back toward the source, potentially damaging equipment.
High standing waves can induce high voltages that stress internal RF components.
Poor VSWR significantly reduces actual radiated power and system range.
Practical RF applications
Antenna system integrity
In real-world deployment, VSWR is the primary health check for antenna systems. Values under 1.5 are target for high-performance base stations, while values above 3.0 often trigger system alarms.
Expert measurement tips
Frequency range
Always measure VSWR across the entire operating bandwidth, not just at the center frequency.
Cable loss
Account for cable attenuation between the meter and the antenna; high loss can mask a poor VSWR at the antenna.
Calibration
Ensure your directional coupler or SWR meter is calibrated for the specific frequency band.
Connector check
80% of high VSWR issues are caused by poorly crimped or loose RF connectors.
Deployment tip: Most cellular systems (50Ω) require specialized impedance matching networks like L-networks or gamma matches to minimize reflections at high power.