Impedance Matching Calculator — Turns Ratio, VSWR & Mismatch Loss
Enter source and load impedances to find the transformer turns ratio for maximum power transfer, along with the reflection coefficient, VSWR, return loss (dB), and power efficiency for the unmatched case.
Ω
Ω
Wind n turns on the secondary for every 1 turn on the primary to match Z_L to Z_S
- 1
Impedance ratio (Z_L ÷ Z_S)
8 ÷ 50 = 0.16 - 2
Turns ratio (n = √(Z_L ÷ Z_S))
√0.16 = 0.4000Wind this many secondary turns for every primary turn to reflect Z_L back to Z_S.
How does this calculator work?
To match source impedance Z_S to load Z_L, use a transformer with turns ratio n = √(Z_L/Z_S). Without a transformer, mismatch Γ = |Z_L−Z_S|/(Z_L+Z_S) causes power loss: efficiency = 1−Γ² = 4Z_SZ_L/(Z_S+Z_L)², return loss = −20log(Γ) dB, VSWR = (1+Γ)/(1−Γ).
Formula
How this is calculated
Maximum power is transferred from source to load when the load impedance equals the complex conjugate of the source impedance. For purely resistive impedances this simplifies to Z_L = Z_S. When they differ, a matching transformer with turns ratio n = √(Z_L/Z_S) reflects the correct impedance (n²·Z_L) back to the source. Common examples: an 8 Ω speaker driven by a 600 Ω amplifier output, a 50 Ω RF transmitter feeding a 75 Ω cable, or an audio transformer bridging studio gear to broadcast lines.
The reflection coefficient Γ = |Z_L − Z_S| / (Z_L + Z_S) quantifies the mismatch on a 0–1 scale: Γ = 0 is a perfect match (all power delivered), Γ = 1 is total reflection (no power delivered). Return loss RL = −20·log₁₀(Γ) is the reflected power expressed in dB — a higher number is better (∞ dB for a perfect match). The voltage standing-wave ratio VSWR = (1+Γ)/(1−Γ) appears in RF work; 1:1 is ideal and below 2:1 is generally acceptable. Mismatch loss = −10·log₁₀(1−Γ²) is the fraction of available power lost to reflection.
This calculator assumes purely resistive (real), frequency-independent impedances. Reactive components and complex impedances at RF frequencies require a network analyser and L/T/Pi-network design using a Smith chart, which is beyond this tool.
Frequently asked questions
Impedance matching ensures maximum power flows from source to load. A mismatch reflects power back toward the source, reducing efficiency and — in RF systems — potentially causing standing waves that can overheat transmitters or damage finals.
In RF work, VSWR below 2:1 (Γ < 0.33, mismatch loss < 0.5 dB) is generally acceptable. VSWR = 1:1 is a perfect match. Values above 3:1 indicate significant reflection and noticeable power loss.
No — it assumes real (purely resistive) impedances. Real antennas, speakers, and transmission lines have complex impedances with reactive parts. For those cases, use a Smith chart or design an L, T, or Pi matching network with a dedicated RF design tool.
Also known as
TG we-Calculate Editorial Team. (2026). Impedance Matching Calculator — Turns Ratio, VSWR & Mismatch Loss [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/impedance-matching-calculator
TG we-Calculate Editorial Team. "Impedance Matching Calculator — Turns Ratio, VSWR & Mismatch Loss." TG we-Calculate. 2026. https://we-calculate.com/calculator/impedance-matching-calculator.
TG we-Calculate Editorial Team, "Impedance Matching Calculator — Turns Ratio, VSWR & Mismatch Loss," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/impedance-matching-calculator
@misc{wecalculate_impedance_matching_calculator, title = {Impedance Matching Calculator — Turns Ratio, VSWR & Mismatch Loss}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/impedance-matching-calculator}}, year = {2026}, note = {TG we-Calculate} }
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