Capacitance Calculator
Design capacitors. Calculate capacitance for parallel plates, spheres, or cylinders based on their dimensions and the insulating material.
C = k × ε₀ × A / d
How the Capacitance Calculator Works
Select the capacitor geometry: parallel plate, spherical, or cylindrical. Enter the dimensions appropriate for your selection: plate area and separation for parallel plate, inner and outer radii for spherical or cylindrical.
Choose the dielectric material between the conductors. The calculator uses the material's relative permittivity (dielectric constant) in the capacitance formula. Common materials like air, paper, glass, and ceramic are included.
Results show the capacitance in farads (typically displayed in μF, nF, or pF for practical values). The calculation steps show the formula with your values substituted. A diagram illustrates the capacitor geometry.
When You'd Actually Use This
Electronic circuit design
Design custom capacitors for specific applications. Calculate required plate area for a target capacitance value in your circuit.
Sensor development
Design capacitive sensors for position, pressure, or humidity. Changes in geometry or dielectric create measurable capacitance changes.
High voltage equipment
Design capacitors for power systems. Calculate capacitance of bushings, cables, and other high voltage components for proper system modeling.
Coaxial cable analysis
Calculate capacitance per unit length of coaxial cables. Important for impedance matching and signal transmission characteristics.
Physics education
Understand how geometry affects capacitance. Explore why larger plates, closer spacing, and higher-k dielectrics increase capacitance.
Energy storage calculations
Estimate energy storage in capacitors. Energy = ½CV². Calculate required capacitance for specific energy storage needs.
What to Know Before Using
Capacitance stores electrical energy.Capacitors store energy in the electric field between conductors. Unlike batteries, they release energy quickly and can charge/discharge rapidly.
Dielectric increases capacitance.Insulating materials between plates increase capacitance by the dielectric constant k. Air has k≈1, ceramics can have k in the thousands.
Smaller separation means more capacitance.Capacitance is inversely proportional to plate separation. But too close risks dielectric breakdown and arcing.
Formulas assume ideal conditions.Parallel plate formula assumes uniform field (plate size ≫ separation). Edge effects (fringing) increase actual capacitance slightly.
Pro tip: Dielectric strength limits operating voltage. Even with high capacitance, a thin dielectric may break down at low voltage. Check both capacitance and voltage rating for your application.
Common Questions
What is a farad?
One farad = one coulomb per volt. It's a huge unit. Practical capacitors are measured in microfarads (μF), nanofarads (nF), or picofarads (pF).
Why do different shapes have different formulas?
Electric field geometry differs. Parallel plates have uniform field. Spherical and cylindrical have radial fields. Gauss's law gives different results for each.
What's the best dielectric material?
Depends on application. Ceramic: high k, good for small capacitors. Film: stable, low loss. Electrolytic: very high capacitance but polarized.
Can capacitance be negative?
No. Capacitance is always positive. It represents the ability to store charge. Negative values would violate energy conservation.
What happens if I exceed breakdown voltage?
The dielectric ionizes and conducts. This can permanently damage the capacitor. Always operate well below the rated breakdown voltage.
How does frequency affect capacitance?
Ideal capacitance is frequency-independent. Real capacitors have parasitic inductance and resistance, making impedance frequency-dependent.
What's permittivity?
Permittivity (ε) measures how a material responds to electric fields. ε = ε₀ × εᵣ, where ε₀ is vacuum permittivity and εᵣ is relative permittivity (dielectric constant).
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