Coaxial Cable Impedance Calculator
Calculate characteristic impedance, velocity factor, propagation velocity, and other transmission line parameters of a coaxial cable.
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Inputs
Live
Math
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Related
Enter parameters and click Calculate to view results
Formula & Theory
Z₀ = (60 / √εr) × ln(D/d)This formula is used to calculate antenna parameters for coaxial cable impedance calculator.
Overview
Coaxial Cable Impedance helps you calculate design values for a waveguide & feedline project from Inner Shield Diameter, Centre Conductor Diameter, Dielectric Constant (εr). Calculate characteristic impedance, velocity factor, propagation velocity, and other transmission line parameters of a coaxial cable. Use the result to make an informed first design decision before choosing hardware, setting dimensions, or evaluating the RF system in its final environment.
Input Guide
Enter Inner Shield Diameter, Centre Conductor Diameter, Dielectric Constant (εr) exactly in the units shown by this coaxial cable impedance. Check the operating band, unit prefix, and decimal position before calculating; these are the inputs used by the formula.
- Inner Shield Diameter — use mm.
- Centre Conductor Diameter — use mm.
- Dielectric Constant (εr).
Output Guide
The results describe the calculated coaxial cable impedance values for the inputs you entered. Check each value against the available space, selected components, feed system, and operating conditions before making a final design decision.
How This Calculator Works
The Coaxial Cable Impedance uses Z₀ = (60 / √εr) × ln(D/d). Supply Inner Shield Diameter (mm), Centre Conductor Diameter (mm), Dielectric Constant (εr) in the displayed units, then use the calculated values as the first engineering target for this waveguide & feedline design or analysis.
Design Notes
This waveguide & feedline calculation is based on Z₀ = (60 / √εr) × ln(D/d). Real-world accuracy depends on factors such as material properties, losses, mounting, nearby conductors, ground interaction, feed-line effects, and construction tolerance. Confirm the final system with measurement or simulation.
Build and Tuning Notes
Apply the coaxial cable impedance result as an initial target, then validate it in the intended installation. Keep the physical layout and feed arrangement consistent while testing, change one parameter at a time, and record the measured outcome before making another adjustment.
Frequently Asked Questions
What does the Coaxial Cable Impedance calculate?
Calculate characteristic impedance, velocity factor, propagation velocity, and other transmission line parameters of a coaxial cable. The calculation provides an initial design value based on Inner Shield Diameter (mm), Centre Conductor Diameter (mm), Dielectric Constant (εr).
Which inputs are needed for the Coaxial Cable Impedance?
Enter Inner Shield Diameter (mm), Centre Conductor Diameter (mm), Dielectric Constant (εr) using the displayed units. Each value directly affects the calculated result, so confirm the unit and operating conditions before running the calculation.
How accurate is this coaxial cable impedance?
It follows Z₀ = (60 / √εr) × ln(D/d). It is accurate for the formula assumptions, but installed performance can change because of materials, loss, environment, mounting, nearby objects, and measurement uncertainty.
What should I do after using the Coaxial Cable Impedance?
Compare the result with the practical constraints of your waveguide & feedline system, then validate the completed design with appropriate measurement equipment or simulation.
Alex Warren
B.Sc. in Electrical & Electronic Engineering (EEE)
Alex specialises in antenna design and wave propagation. His expertise helps ensure these calculators present practical RF concepts, useful design estimates, and clear engineering guidance for students, HAM operators, and wireless professionals.