What is the formula for a parallel-plate capacitor?

C = ε₀ × εᵣ × A / d, where ε₀ = 8.854 × 10⁻¹² F/m is the permittivity of free space, εᵣ is the relative permittivity of the dielectric, A is the plate area in m², and d is the plate separation in meters.

What is relative permittivity (dielectric constant)?

Relative permittivity (εᵣ) describes how much a material increases the capacitance compared to a vacuum (εᵣ = 1). Air is ≈1.0006, glass is 4–10, and ceramics used in capacitors can exceed 10,000.

Why does larger plate area increase capacitance?

A larger area allows more charge to be stored for the same voltage. Capacitance is directly proportional to area (C ∝ A).

Why does a smaller gap increase capacitance?

A thinner dielectric means the electric field is stronger for the same charge, allowing more charge storage. Capacitance is inversely proportional to plate separation (C ∝ 1/d).

What units is capacitance measured in?

Capacitance is measured in Farads (F). Practical capacitors are typically rated in picofarads (pF = 10⁻¹² F), nanofarads (nF = 10⁻⁹ F), or microfarads (µF = 10⁻⁶ F).

Capacitance Calculator

Name: Capacitance Calculator
Availability: InStock
Author: Nham Vu

Enter the plate area, separation distance, and relative permittivity to instantly calculate the capacitance of a parallel-plate capacitor using C = ε₀εᵣA/d.

Capacitance Calculator

Plate Area (A)

Plate Separation (d)

Dielectric (εᵣ)

Enter plate area, separation, and dielectric — then click Calculate.

Capacitance

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All Units

Common Dielectric Materials

Material	εᵣ (typical)

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Summary

Enter the plate area, separation distance, and relative permittivity to instantly calculate the capacitance of a parallel-plate capacitor using C = ε₀εᵣA/d.

How it works

Enter the plate area in your preferred unit (mm², cm², m², or in²).
Enter the separation distance between the plates (mm, cm, m, or in).
Select or enter the relative permittivity (εᵣ) of the dielectric material.
Click Calculate to compute the capacitance using C = ε₀εᵣA/d.
View the result in Farads plus cross-conversions to pF, nF, and µF.

Use cases

Design parallel-plate capacitors for analog and RF circuits.
Estimate capacitance of PCB trace-to-plane structures.
Verify capacitor dimensions against a target capacitance value.
Compare different dielectric materials for a fixed plate geometry.
Educational demonstration of how geometry affects capacitance.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu