Characteristic Impedance

Calculate coax characteristic impedance using Z₀ = (59.959 / √εr) · ln(b/a).

RF Tools • Coax Z₀

Solve for Z₀ (Ω)

Dielectric constant εr Typical: PTFE ~ 2.1, PE ~ 2.25 Outer conductor inner radius b

b and a must be in the same units. Inner conductor radius a

same

Must be smaller than b (b/a > 1).

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Enter εr, b, and a to compute Z₀.

Target impedance Z₀ (Ω) Common: 50Ω, 75Ω Dielectric constant εr Used to compute ln(b/a) then b/a.

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Enter Z₀ and εr to compute b/a.