Permittivity Converter
Permittivity describes how a material responds to an electric field, with the SI unit of farads per meter (F/m). Absolute permittivity is small in SI terms, so it is often quoted in picofarads or microfarads per meter. Relative permittivity (the dielectric constant) is dimensionless and equals the absolute permittivity divided by the vacuum permittivity. This converter handles F/m, pF/m, uF/m, and relative permittivity, using the CODATA vacuum permittivity of 8.8541878128e-12 F/m to bridge the dimensionless and absolute forms.
Permittivity conversion
Base value (F/m) = input * factor(from unit)
Output = base value / factor(to unit)
1 pF/m = 1e-12 F/m
1 uF/m = 1e-6 F/m
relative * 8.8541878128e-12 F/m = absolute permittivity
Relative permittivity (dielectric constant) is dimensionless; multiplying by the vacuum permittivity (8.8541878128e-12 F/m) gives the absolute permittivity in F/m.
Permittivity context
- The SI unit of permittivity is the farad per meter (F/m).
- The vacuum permittivity is 8.8541878128e-12 F/m per the CODATA recommended value.
- Relative permittivity (the dielectric constant) is the ratio of a material's permittivity to the vacuum value.
- Vacuum has a relative permittivity of exactly 1; water is near 80 at room temperature.
- Permittivity sets the capacitance of a capacitor for a given geometry.
Permittivity: frequently asked questions
What is relative permittivity?
Relative permittivity, also called the dielectric constant, is the ratio of a material's absolute permittivity to the permittivity of free space. It is dimensionless: vacuum is 1, dry air is just above 1, and water is near 80 at room temperature.
What value of vacuum permittivity is used?
The CODATA recommended value of 8.8541878128e-12 F/m. The converter uses it to translate between dimensionless relative permittivity and absolute permittivity in F/m.
Why is permittivity so small in F/m?
Because the farad is a very large unit of capacitance. Absolute permittivities are on the order of 1e-11 to 1e-9 F/m, which is why picofarads per meter is a convenient practical unit.
How does permittivity relate to capacitance?
For a parallel-plate capacitor, capacitance equals permittivity times plate area divided by separation. A higher permittivity dielectric stores more charge at the same voltage.
Is permittivity the same as permeability?
No. Permittivity governs the electric response of a material (F/m), while permeability governs the magnetic response (H/m). They are distinct quantities, though both appear in the speed of light relation.
Official sources
- NIST: CODATA Recommended Values of the Fundamental Physical Constants.
- NIST Special Publication 811: Guide for the Use of the International System of Units.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.