Please enter all required values.
RESULTS
Input Parameters Specification
Wire DiameterRound conductor diameter used in the wire microstrip impedance formula. Larger wire diameter normally reduces impedance.
Substrate HeightDistance from the wire conductor to the reference plane. This height strongly affects characteristic impedance.
Dielectric ConstantRelative permittivity of PCB dielectric material. Higher dielectric constant usually lowers impedance.
OutputCharacteristic impedance in ohms for RF PCB and wire-over-ground transmission line design.
Practical Operational Examples
RF Wire Routing
Estimate impedance for a round wire running above a PCB ground plane or dielectric substrate.
Stackup Tuning
Change wire diameter, dielectric height or Er to tune impedance toward a practical RF target.
Lab Fixture Design
Useful for simple RF fixtures, jumper-style conductors, prototype transmission lines and test layouts.
Material Comparison
Compare FR4, PTFE, ceramic and other dielectric constants to see how impedance changes.
Diagrams & Theory
A wire microstrip uses a round conductor above a dielectric substrate and ground plane. Its impedance changes with wire diameter, substrate height and dielectric constant.
Formulas & Mathematical Logic
Effective Er = (Er + 1) / 2 + (Er - 1) / 2 × correction factor.
A = (2 × H + D) / D.
Z0 = 377 / (2 × π × sqrt(effective Er)) × log(A + sqrt(A² - 1)).
D = wire diameter, H = substrate height, Er = dielectric constant.
Practical meaning: larger diameter lowers impedance, while larger height above ground increases impedance.
Step-by-Step Example
Example: wire diameter = 10 mil, substrate height = 60 mil, dielectric constant = 4.2.
The calculator converts wire diameter and substrate height using the selected unit multipliers.
Effective dielectric constant is calculated from Er, diameter and height relationship.
A is calculated as (2 × H + D) / D.
Impedance is calculated using the logarithmic transmission line expression.
The final result is displayed in ohms.
How to Use This Calculator
Enter wire diameter and select the correct unit.
Enter substrate height from the wire to the reference plane.
Enter dielectric constant of the PCB material.
Click Calculate to get wire microstrip impedance.
Compare the result with your RF impedance target such as 50 Ω.
About This Calculator
Estimate impedance for round-wire microstrip transmission structures.
The CalcBoy Wire Microstrip Impedance Calculator calculates characteristic impedance using wire diameter, substrate height and dielectric constant.
A wire microstrip is a round conductor placed above a dielectric substrate with a reference ground plane below. This type of structure can appear in RF prototypes, jumper-wire experiments, test fixtures, special interconnects, antenna feeds and lab transmission line setups where a normal flat PCB microstrip trace is not the exact geometry.
The impedance depends mainly on conductor diameter, height above the reference plane and dielectric constant. A larger wire diameter usually reduces impedance because the conductor becomes electrically larger. A greater height above ground usually increases impedance. A higher dielectric constant lowers wave velocity and changes the impedance result.
This calculator is useful for RF PCB work, microwave prototyping, controlled impedance experiments and quick geometry checks. For critical RF or production designs, validate with field solver results, measured test coupons, PCB manufacturer stack-up data or lab measurement.
Best UseRound-wire microstrip impedance estimates for RF and PCB prototypes.
Supported InputsWire diameter, substrate height and dielectric constant.
Helpful ForRF fixtures, jumper-wire transmission lines, antenna feeds and lab testing.
Design ReminderUse measured stack-up data for accurate impedance control.
Tip: For RF work, the return path below the wire matters. Keep the ground reference continuous and close to reduce unexpected impedance changes.
Frequently Asked Questions
What is wire microstrip impedance?
It is the characteristic impedance of a round conductor above a dielectric substrate and reference ground plane.
What inputs are required?
The calculator needs wire diameter, substrate height and dielectric constant.
Does larger wire diameter lower impedance?
Generally yes. Increasing wire diameter lowers the calculated impedance in this geometry.
Why does substrate height matter?
Substrate height changes the electric field geometry between the wire and reference plane, which affects impedance.
Can this be used for 50 ohm RF design?
Yes, it can help estimate geometry near 50 Ω, but final RF layouts should be verified with measurement or simulation.
What unit is the result?
The impedance result is displayed in ohms.
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