Capacitor Calculator: Parallel Plate Capacitance, Series and Parallel Capacitors, Charge and Energy

Capacitance of plates and groups of capacitors, with charge and stored energy.

Calculated from standard textbook formulas, with every step shown. The formulas are fixed, so the working does not need checking: what matters is the numbers you type in. Use these calculators only if you are competent to choose the inputs (loads, material strength, dimensions, supports) and check your units and assumptions. For learning and checking your own working: design and sign-off are for a qualified engineer. Drafting Central does not store the numbers you type.

How this calculator works

Choose a plate capacitor or a group of capacitors.

For a plate capacitor enter the area, the gap and the relative permittivity. For a group enter up to three capacitances.

Enter the voltage to get the charge and the energy stored.

Formulas used

  • C = \frac{\varepsilon_r\varepsilon_0A}{d}
  • C_{par} = C_1 + C_2 + C_3
  • \frac{1}{C_{ser}} = \frac{1}{C_1} + \frac{1}{C_2} + \frac{1}{C_3}
  • Q = CV,\quad E = \tfrac12CV^2

Worked example

With the default numbers in the calculator above:

  1. Capacitance of the parallel plate capacitor: 88.54 pF (8.8542e-5 uF)
  2. Charge stored at the voltage you gave: 1.06 nC
  3. Energy stored: 0.0064 uJ
  4. Electric field between the plates: 12.00 kV/m

Change the numbers in the calculator to see the full working, every step, for your own case.

A second worked example

A different case, with these numbers: What do you want? Capacitors in series and parallel.

  1. Capacitors in parallel (the capacitances add): 60.00 uF
  2. Capacitors in series (the reciprocals add): 5.45 uF
  3. Charge and energy at the voltage you gave, for the parallel bank: 720.00 uC and 4.32 mJ
  4. Charge and energy at the same voltage, for the series bank: 65.45 uC and 0.39 mJ

Common questions

How do I add capacitors in series?

Add the reciprocals: 1/C = 1/C1 + 1/C2 + ... The total is smaller than the smallest capacitor.

How do I add capacitors in parallel?

Add the capacitances. The total is larger than the largest capacitor.

How much energy does a capacitor store?

E = half C V squared.

What does the dielectric do?

It multiplies the capacitance by its relative permittivity, because it reduces the field between the plates.

Related calculators

Got a question about this? Ask an engineering question and get a plain-language answer with references.

Further reading: Any first-year physics or electrical text (capacitance).

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