Parallel-Plate Capacitor
Computes the capacitance of a parallel-plate capacitor from the overlapping plate area, the gap between plates, and the dielectric constant of the material between them. A multi-plate stack of N plates acts like N−1 capacitors in parallel. Enter an applied voltage to also see the electric field and the stored energy. (This is the ideal formula; real capacitors add fringing at the plate edges.)
Equations & Parameters ▸
\(C = \dfrac{\varepsilon_0\,\varepsilon_r\,A\,(N-1)}{d} \qquad E = \dfrac{V}{d} \qquad U = \tfrac{1}{2}C V^2\)
| A | Overlapping plate area (mm²). |
| d | Separation between adjacent plates (mm). |
| εr | Relative permittivity: air ≈ 1, FR-4 ≈ 4.4, mica ≈ 6, alumina ≈ 9.8, class-I ceramic 15–100. |
| N | Number of plates (2 for a simple capacitor). A stack of N plates gives N−1 gaps in parallel. |
| ε0 | Permittivity of free space = 8.854×10⁻¹² F/m. |
References: D. K. Cheng, Field and Wave Electromagnetics, 2nd ed., Addison-Wesley, 1989. · D. M. Pozar, Microwave Engineering, 4th ed., Wiley, 2012.
Inputs
mm²
Overlap areamm
Plate gap1 = air
Default 2
V
For field/energyResults
Capacitance
Capacitance C—
C per gap—
At applied voltage
Electric field—
Stored energy—
Charge—
Diagram