This capacitance calculator is a handy tool when designing a parallel plate capacitor. Such a capacitor consists of two parallel conductive plates separated by a dielectric (electric insulator that can be polarized). Read on if you want to find out what capacitance is, and how to calculate it using the capacitance equation.

What is capacitance?

It is the ability of an object to store an electric charge. It only depends on the geometry of the capacitor and the choice of the dielectric material between the plates. In most cases, it does not depend on the potential difference or the charge stored on the plates.

Demonstration capacitor consisting of two parallel metal plates and air as the dielectric
Demonstration capacitor consisting of two parallel metal plates and air as the dielectric.
(Hannes Grobe / CC BY)

Capacitance equation

How to calculate the capacitance, then? You need to use the following formula:

C = εA/s

where:

  • C is the capacitance. It is measured in farads (symbol: F);
  • ε is the dielectric permittivity (a measure of resistance) in farads per meter;
  • A is the area where the plates overlap; and
  • s is the separation distance between the plates.

The permittivity depends on the dielectric material used. By default, this capacitance calculator uses the value of 8.854 pF/m, which is the permittivity of vacuum. If you wish to change this value, click on the advanced mode button.

💡 One picofarad (pF) is equal to 10⁻¹² farads.

How to use the parallel plate capacitor calculator

  1. Determine what material will be used as the dielectric between two plates. In this example, we will use a vacuum.
  2. Once you decide on the material, find out its permittivity - for a vacuum, the value is 8.854 pF/m.
  3. Choose the area of plates. Let's say it's 120 mm².
  4. Measure the distance between the plates - we will assume 5 mm.
  5. Insert all values into the capacitance calculator. It will find the value of capacitance for you! In our example, it is equal to 0.212 pF.
  6. You can check the correctness of calculations with the capacitance equation.

What next?

Once you've calculated the capacitance of a single parallel plate capacitor, you can join it with other capacitors in series or in parallel. It is fairly easy to calculate the total capacitance of such a system:

Interested in electricity? Check out our Ohm's law calculator.

Bogna Haponiuk