Capacitance Calculator

Understanding Capacitance Calculator

Capacitance relates the electric charge stored to the voltage across a capacitor. The fundamental relationship is Q = CV.

How to use this calculator

1. Choose which value you want to find, charge, capacitance, or voltage.
2. Enter the two values you already know.
3. Make sure the units match, for example coulombs, farads, and volts.
4. Use the result to check your circuit or finish your homework problem.

The formula explained

The formula \(Q = C \times V\) computes the charge \(Q\) stored in a capacitor from its capacitance \(C\) and voltage \(V\). You can rearrange it to find \(C = \frac{Q}{V}\) or \(V = \frac{Q}{C}\).

• Q = charge, measured in coulombs \(\text{C}\)
• C = capacitance, measured in farads \(\text{F}\)
• V = voltage, measured in volts \(\text{V}\)

Step by step method

1. Write down the formula \(Q = C \times V\).
2. Substitute the known values, or rearrange the formula if you are solving for \(C\) or \(V\).
3. Do the arithmetic and include the correct unit.
4. Check that the answer makes sense, especially if the voltage or capacitance is very large or very small.

Worked example

Problem. A capacitor has a capacitance of \(0.004\,\text{F}\) and a voltage of \(12\,\text{V}\). Find the charge.

1. Use \(Q = C \times V\).
2. Substitute the values, \(Q = 0.004 \times 12\).
3. Calculate \(Q = 0.048\,\text{C}\).

Tips and common mistakes

• Be careful with units, because \(1\,\text{mF} = 0.001\,\text{F}\) and \(1\,\mu \mathrm{F} = 0.000001\,\text{F}\).
• If you solve for voltage or capacitance, divide instead of multiplying, and double-check that you used the correct known values.

Frequently asked questions