Capacitance Calculator
Capacitance quantifies the ability of an electrostatic component to store electric charge across an electric field per unit voltage (C = Q / V). For parallel-plate capacitors, capacitance depends directly upon plate surface area, dielectric permittivity, and plate separation gap (C = ε₀·εᵣ·A / d). This calculator computes capacitance, total stored Coulombs, electrostatic energy, and AC reactance.
Surface area of each conductive capacitor plate in square centimetres (cm²)
Distance between the parallel conducting plates in millimetres (mm)
Relative permittivity (dielectric constant εᵣ) of insulating barrier
Potential difference applied across the capacitor terminals in Volts (V)
Alternating current frequency in Hertz (Hz) for capacitive reactance
Capacitance value in picofarads (1 pF = 10⁻¹² F)
How to Use This Calculator
- Enter plate surface area in square centimetres.
- Input the distance between plates in millimetres.
- Select the dielectric insulating medium (e.g. ceramic, mica, air).
- Enter working voltage and AC frequency to evaluate stored energy and impedance.
Formula & Calculation Methodology
Capacitance scales with plate area (A) and relative dielectric constant (εᵣ), and is inversely proportional to separation distance (d). Stored charge equals capacitance times voltage. In AC circuits, capacitor impedance decreases as frequency increases.
Worked Example
Parallel plates of 100 cm² separated by 1.0 mm with high-K ceramic dielectric at 50V, 60Hz
Frequently Asked Questions
What role does the dielectric material play inside a capacitor?↓
Dielectrics contain polar molecules that align against the electric field. This polarization partially neutralizes surface charge, allowing more charge to accumulate at the same voltage and multiplying capacitance by factor εᵣ.
Why does capacitive reactance decrease at higher AC frequencies?↓
As alternating current alternates faster, charge cycles back and forth without having time to fully saturate the capacitor plates, presenting less opposing back-EMF and lower effective impedance (Xc = 1 / 2πfC).
What causes capacitor dielectric breakdown?↓
If applied voltage exceeds the dielectric strength of the insulator material, electric fields rip electrons free from atoms, causing catastrophic arcing and permanent short-circuit failure.
What limitation applies regarding fringe electric fields?↓
The standard parallel-plate formula assumes an idealized uniform electric field. In reality, fringing electric fields curve outward around plate edges, causing actual capacitance to be slightly higher when plate separation d is large relative to plate width.
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Source Citation & Disclaimer
Informational tool only; not licensed tax, legal, or financial advice.