Calculate a parallel-plate capacitor's capacitance from its geometry and the insulating material between the plates.

How to Use the Parallel Plate Capacitance Calculator

Enter the plate area and the gap between the plates, each with its own unit choice, then pick a dielectric material from the dropdown — or select Custom to type in your own relative permittivity. Capacitance updates immediately and auto-scales to whichever unit, farads down to picofarads, actually fits the number.

Two parallel conductive plates separated by an insulator make one of the simplest capacitors there is, and it's also the one that most directly exposes what capacitance physically depends on: how much plate area faces itself, how close together the plates sit, and what's filling the gap between them. All three variables sit in one equation:

C = ε₀ × εr × A ÷ d

ε₀, the vacuum permittivity, is a fixed physical constant — 8.854 × 10⁻¹² F/m — that sets the baseline for how well empty space itself supports an electric field. εr, relative permittivity (also called the dielectric constant), scales that baseline up depending on the insulating material sitting between the plates.

The Dielectric Does Most of the Work

Swap air for a real insulator and capacitance jumps by whatever factor that material's εr represents — mica at roughly 6 stores about six times the charge of an air-gapped capacitor with identical geometry. That's the entire reason capacitors are packed with dielectric material rather than left as bare air gaps: it lets a physically small component reach a useful capacitance instead of needing plates the size of dinner tables.

The presets here — paper, mica, glass, a "typical ceramic" figure — are illustrative starting points, not universal constants the way ε₀ is. Real material grades vary: ceramic capacitor dielectrics alone span from around 6 up into the thousands depending on the exact formulation, which is why the ceramic preset here is labeled as one typical low-k example rather than a catch-all figure. For anything that has to match a real datasheet, use the Custom option and enter the manufacturer's stated εr.

Separation sits in the denominator, so it works against you if it grows — halve the gap between plates and capacitance doubles, all else equal. That's also the practical limit on how far this formula can be pushed: real capacitors can't shrink the gap indefinitely without the dielectric breaking down under the operating voltage.