How this calculator works
Wide plates separated by a narrow uniform gap have an approximately uniform field between them. A dielectric increases capacitance by its relative permittivity: absolute permittivity equals epsilon0 times that ratio. This model neglects fringing, leakage and dielectric breakdown. The vacuum default is the CODATA 2022 value, 8.8541878188e-12 F/m.
Formula
C = epsilon A/d. Rearrangements are A = Cd/epsilon, d = epsilon A/C and epsilon = Cd/A.
Worked example
Vacuum plates with overlap area 0.01 m² and separation 0.001 m have capacitance 8.85419e-11 F, or about 88.54 pF. Doubling the area doubles this value.
Frequently asked questions
Is permittivity the same as relative permittivity?
No. Multiply relative permittivity by the vacuum value to obtain the F/m input.
Which area should I enter?
Enter the overlapping face area of one plate, rather than adding both plate areas.
What happens at zero separation?
The ideal formula becomes singular. A real device would contact or break down; the calculator requires a positive separation.