Capacitance Calculator
Enter the charge a capacitor stores and the voltage across it to get the capacitance in farads — plus the same value in microfarads — from C = Q / V.
Use SI units
Charge in coulombs and voltage in volts give capacitance in farads — most real capacitors land in the microfarad (µF) or picofarad (pF) range.
What is capacitance?
Charge stored per volt
Capacitance is a measure of how much electric charge a component can store for each volt applied across it. A capacitor with a high capacitance holds a lot of charge at a modest voltage; one with a low capacitance holds little. The capacitance calculator turns two measurements — the charge in coulombs and the voltage in volts — into the capacitance in farads, alongside the same figure expressed in microfarads, which is the unit printed on most real-world parts. It is the number behind timing circuits, power-supply smoothing, audio filters, and energy storage on a circuit board.
Enter the charge in coulombs and the voltage in volts to get the capacitance in farads and microfarads instantly.
Capacitance is simply the stored charge divided by the voltage across the capacitor.
C = Q / VThe relationship is linear: for a fixed capacitor, doubling the charge doubles the voltage, so the ratio stays the same. Use coulombs for charge and volts for voltage and the capacitance comes back in farads. Because one farad is a very large unit, the calculator also gives the result in microfarads (one farad equals 1,000,000 µF), which matches the values you will read off most components.
Suppose a capacitor stores a charge of 0.001 C when 10 V is applied across it.
Take the charge and voltage
Charge Q = 0.001 C and voltage V = 10 V — the two values you measure.
Divide charge by voltage
0.001 ÷ 10 = 0.0001 — the capacitance in farads.
Convert to microfarads
0.0001 F × 1,000,000 = 100 µF — the same capacitance in the unit printed on the part.
The farad value is the fundamental answer, but it is almost always a tiny fraction of one because the farad is such a large unit. That is why the microfarad reading is usually the more useful one in practice: a 100 µF electrolytic capacitor, a 10 µF film capacitor, or a 0.1 µF ceramic decoupling capacitor are all everyday parts, while a full farad is reserved for large supercapacitors. A higher capacitance means the part stores more charge at the same voltage, so it can supply more current before its voltage sags — handy for smoothing a power rail or holding up a circuit during a brief dip. Reading the result the other way round, if you know the capacitance and the voltage you can find the stored charge, and from there the stored energy; capacitance is the bridge between the two.
The formula is exact, but a couple of practical points are worth keeping in mind.
Ideal capacitor and consistent units
This calculator treats the capacitor as ideal, with a capacitance that does not change with voltage. Real parts drift with temperature, ageing, and applied voltage — class-2 ceramics in particular lose capacitance under bias — so treat the figure as nominal. Keep your units consistent: coulombs for charge and volts for voltage, or the farads will be wrong. The voltage must be greater than zero, since dividing a stored charge by zero volts is undefined.