What is the characteristic impedance of vacuum?

The characteristic impedance of free space is Z_0 = 376.730313668 Ω (uncertainty ±5.7e-8), close to 120π Ω ≈ 377 Ω.

Key facts

Frequently asked questions

What is the impedance of free space?

Z_0 = 376.730313668 Ω, the ratio of electric to magnetic field magnitude of a plane wave in vacuum.

Is the vacuum impedance 377 ohms?

It is about 376.73 Ω, often approximated as 120π Ω ≈ 377 Ω in antenna and RF engineering.

How is Z_0 defined?

Z_0 = μ₀·c = sqrt(μ₀/ε₀), linking it to permeability, permittivity, and the speed of light.

Related pages

• Speed of light
• Planck constant
• Reduced Planck constant
• Avogadro constant
• Boltzmann constant
• Molar gas constant
• Elementary charge
• Gravitational constant

Impedance of vacuum is part of PhysRef on GOAT Lab — a free reference you can use without signing up, and it works offline. Open the tool above for any custom value.

Advertise

Part of GOAT Lab — 26 free, browser-based science, engineering and developer tools. No sign-up.