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Coaxial Characteristic Impedance Calculator
Calculate the lossless TEM characteristic impedance of a concentric coaxial line from its conductor radii and uniform dielectric properties. Choose input units and calculate one value within the stated conditions.
Inputs
Calculations run in this browser. Scientific notation such as 1.2e-3 is supported. Do not group thousands.
Result
Characteristic impedance Z₀
Enter values and select Calculate.
Z₀ = [√(μ₀μr/(ε₀εr))/(2π)] ln(b/a)
Assumptions
Required: perfect concentric cylindrical conductors, a uniform linear dielectric and lossless TEM propagation. Both dimensions are radii: a is the outer surface of the inner conductor and b is the inner surface of the shield, with b > a. Excluded: skin effect, conductor and dielectric loss, dispersion, higher modes and eccentricity. Characteristic impedance differs from DC resistance and the input impedance of a finite cable.
Displayed values are floating-point approximations. Design safety factors and unprovided error contributions are not calculated.
Formula references and credits
NaNa Lab created the code, descriptions, icons and preview images. Text, figures and code from the linked references have not been reproduced.
Physical constants: NIST / CODATA 2022. The values of μ₀ and ε₀ are measured recommendations, not exact defining constants. Values and precision notes are in the source record.
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