Return Loss Calculator
Convert between return loss, reflection coefficient and VSWR, and see the reflected power, transmitted power and mismatch loss, with a response chart, a live wave diagram and reference tables of real-world values.
Every 6 dB halves |Γ|
Return loss is a 20·log scale on voltage. +6 dB halves the reflected voltage and +10 dB cuts reflected power to one tenth.
Higher RL = better match
A large RL means little power comes back. RL → ∞ is a perfect match; 0 dB is a total reflection (open or short).
Mismatch loss is small
Even at 10 dB RL only 10% of power is reflected, costing about 0.46 dB, but reflections still distort signals and can stress transmitters.
Sign convention
RL is quoted as a positive number of dB. In S-parameters S11 (dB) = −RL, so a 20 dB return loss is S11 = −20 dB.
Real-world examples
Typical specification values you meet in practice, with every column computed from the formula. Click Load to open one in the calculator.
| Application | Typical spec | RL (dB) | |Γ| | VSWR | Reflected power | Mismatch loss (dB) |
|---|
Return loss conversion table
| RL (dB) | |Γ| | VSWR | Reflected power | Transmitted power | Mismatch loss (dB) |
|---|
Impedance mismatch examples (Z₀ = 50 Ω)
| ZL (Ω) | |Γ| | RL (dB) | VSWR | Reflected power |
|---|
Formulas
|Γ| = 10^(−RL/20)
VSWR = (1 + |Γ|) / (1 − |Γ|)
|Γ| = (VSWR − 1) / (VSWR + 1)
Reflected power = |Γ|²
Mismatch loss = −10·log₁₀(1 − |Γ|²)
Results assume a single frequency and a passive load. They are estimates for quick design checks, not a replacement for measured S-parameters.
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| RL | Return loss (ratio of incident to reflected power) | dB |
| Γ | Reflection coefficient (complex) | dimensionless |
| |Γ| | Magnitude of the reflection coefficient (between 0 and 1) | dimensionless |
| log₁₀ | Common (base‑10) logarithm | — |
What it means
Return loss (RL) is a measure of the reflection from a load, expressed in decibels. It is defined as RL = −20·log₁₀|Γ|, where Γ is the reflection coefficient. A higher return loss indicates better matching (less reflected power). For example, RL = 20dB means the reflected power is 1% of the incident (|Γ| = 0.1). Return loss is used to evaluate the quality of impedance matching in RF systems, such as antennas, filters, and amplifiers. Example: If |Γ| = 0.2, then RL = −20·log₁₀(0.2) ≈ 13.98 dB. An RL of 20 dB or more is considered good. Return loss is often measured with a network analyser.
Worked example
Return Loss – Practical Example
Real‑World| Parameter | Value |
|---|---|
| |Γ| | 0.2 |
| Formula | RL = −20·log₁₀(|Γ|) |
Common mistakes
Watch unit consistency and the assumptions behind the formula; misapplying it outside its valid conditions is the most frequent error.Applications
Return loss (RL) = −20·log₁₀|Γ| expresses reflected power in decibels. Higher RL means better matching. Engineers use it to specify VSWR requirements, to evaluate antennas, and to ensure efficient power transfer. RL is a standard specification for RF components and systems.
- RF component specification (e.g., connectors, cables)
- Antenna and transmission line performance verification
- Impedance matching quality assessment
- System design and power budget analysis
- Educational understanding of return loss
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