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Capacitance Calculator

Work out capacitance instantly with clear inputs, formula shown and shareable results.

About Capacitance Calculator

Parallel-plate capacitance is permittivity times area divided by separation: C = e0 x er x A / d. Capacitance rises with plate area and dielectric constant and falls with spacing, but reducing spacing also raises field strength, which is what sets the voltage rating.

Formula

Parallel plate capacitance

C = e0 x er x A / d, e0 = 8.854e-12 F/m

Worked example

With the default values below, Capacitance Calculator returns Capacitance of 7.97. Change any input above and every figure here is recalculated in your browser.

Inputs used

Plate area
0.02 m²
Plate separation
0.1 mm
Relative permittivity
4.5
Applied voltage
50 V

Results

Capacitance
7.97 nF
Charge stored
398.44 nC
Energy stored
9.96 µJ
Electric field strength
0.50 kV/mm

Step by step

  1. 1Values used
  2. 2Parallel plate capacitance
  3. 3Capacitance= 7.97 nF
  4. 4Charge stored= 398.44 nC
  5. 5Energy stored= 9.96 µJ
  6. 6Electric field strength= 0.50 kV/mm

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Why do real capacitors use thin films?

Because C is inversely proportional to separation. Micron-thick dielectrics give large capacitance in small volume, limited only by dielectric strength.

What limits the voltage rating?

The field strength V/d must stay well below the dielectric breakdown strength, typically with a safety factor of two or more.

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