What is the vacuum permittivity (ε₀)?
The vacuum electric permittivity is ε₀ = 8.8541878128e-12 F/m (uncertainty ±1.3e-21). It appears in Coulomb's law and the constant 1/(4πε₀).
Open the interactive PhysRef tool →Key facts
| Value | 8.8541878128e-12 F/m |
|---|---|
| Symbol | ε₀ |
| Uncertainty | ±1.3e-21 F/m |
| Relation | c^2 = 1/(ε₀·μ₀) |
| Source | CODATA 2018 |
Frequently asked questions
What is the value of the vacuum permittivity?
ε₀ = 8.8541878128e-12 farads per metre, also called the electric constant.
Is ε₀ exact?
No longer. Since the 2019 SI redefinition ε₀ has a small measured uncertainty of ±1.3e-21 F/m.
How is ε₀ related to the speed of light?
It satisfies c^2 = 1/(ε₀·μ₀), linking electricity, magnetism, and light.
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