Capacitance
Calculate parallel plate capacitance with C=ε₀εᵣA/d. Free calculator with 14 dielectric presets, charge Q=CV, energy E=½CV², and material comparison charts.
About This Calculator
The Capacitance Calculator computes the capacitance of a parallel plate capacitor using the fundamental formula C = ε₀ × εᵣ × A / d. It is designed for physics students, electronics engineers, hobbyists, and anyone who needs to determine the capacitance of a parallel plate geometry with various dielectric materials.
The calculator also computes the stored charge (Q = C × V) and stored energy (E = ½ × C × V²) when a voltage is applied, providing a complete picture of the capacitor's electrical characteristics.
The formula is derived from Gauss's law and the definition of capacitance. The vacuum permittivity ε₀ (8.854 × 10⁻¹² F/m) is a fundamental constant, while the relative permittivity εᵣ depends on the dielectric material placed between the plates. The calculator includes 14 preset dielectric materials ranging from vacuum (εᵣ = 1) to barium titanate (εᵣ ≈ 1200), with a comparison chart to visualize how different materials affect capacitance.
For parallel plate capacitors, the electric field between the plates is approximately uniform (ignoring edge effects), and the capacitance depends only on geometry and the dielectric material. This makes the parallel plate capacitor an ideal starting point for understanding capacitance in more complex geometries such as cylindrical and spherical capacitors.
Regional Notes
- India (IN): Capacitors are widely used in power electronics, motor starting circuits, and consumer electronics. Standard capacitor values follow the IEC 60063 E-series (E6, E12, E24), and dielectric materials like polyester and ceramic are common in Indian electronics manufacturing.
- United States (US): Capacitors are specified per EIA standards. Common applications include power supply filtering, timing circuits, and energy storage in pulsed power systems. The NEC and UL standards govern capacitor ratings for safety in electrical installations.
- United Kingdom (UK): BS EN 60384 series standards specify fixed capacitors for electronic equipment. The IET Wiring Regulations (BS 7671) govern capacitor usage in power factor correction and electrical installations across the UK.
Frequently Asked Questions
How do you calculate capacitance?
Capacitance is calculated using the parallel plate formula C = ε₀ × εᵣ × A / d, where ε₀ is the vacuum permittivity (8.854 × 10⁻¹² F/m), εᵣ is the dielectric constant of the material between the plates, A is the plate area in square meters, and d is the plate separation in meters.
What is the dielectric constant?
The dielectric constant (relative permittivity, εᵣ) measures how well a material can store electrical energy in an electric field relative to vacuum. Vacuum has εᵣ = 1, air is approximately 1, glass is about 4.7, and water is about 80. Higher dielectric constants allow greater capacitance for the same plate geometry.
What units is capacitance measured in?
Capacitance is measured in farads (F), named after Michael Faraday. One farad is very large, so practical capacitors are rated in microfarads (µF, 10⁻⁶ F), nanofarads (nF, 10⁻⁹ F), or picofarads (pF, 10⁻¹² F). This calculator reports capacitance in all four units for convenience.
How does plate area affect capacitance?
Capacitance is directly proportional to the plate area. Doubling the plate area doubles the capacitance because there is more surface area to store electric charge. This relationship is linear in the parallel plate formula C ∝ A.
How does plate separation affect capacitance?
Capacitance is inversely proportional to the distance between plates. Halving the separation doubles the capacitance, while doubling the separation halves it. This is because the electric field strength increases when the plates are closer together, allowing more charge storage at the same voltage.
How do you calculate stored charge and energy?
The stored charge is calculated using Q = C × V, where V is the applied voltage. The stored energy is calculated using E = ½ × C × V², measured in joules. These formulas assume the capacitor is fully charged and operating within its voltage rating.
What is vacuum permittivity?
Vacuum permittivity (ε₀), also called the electric constant, is a fundamental physical constant with a value of approximately 8.854 × 10⁻¹² farads per meter. It describes how an electric field propagates through a vacuum and appears in the capacitance formula, Coulomb's law, and Maxwell's equations.
Can I share my capacitance calculation results?
Yes, all input values are saved in the URL as query parameters. When you calculate, the URL updates automatically. Copy the URL from your browser's address bar to share the exact calculation setup with others. Opening that URL will restore all values and auto-calculate the results.