How do I calculate capacitance from charge and voltage?

Divide stored charge by voltage. Use consistent SI units for farads, coulombs and volts.

What is the energy stored in a capacitor?

Stored energy grows with capacitance and with the square of voltage, so higher-voltage capacitors deserve extra care.

Do capacitors add like resistors?

No. Capacitors add directly in parallel and by reciprocal values in series.

Capacitor Calculator

Calculate capacitance, charge, voltage, stored energy, series or parallel capacitor networks, and RC timing estimates.

Capacitors can retain dangerous voltage after power is removed. Discharge through an appropriate resistor and verify voltage before handling.

Solve for

Capacitance

Voltage, V

Results

Capacitance

100 nF

Voltage

12 V

Charge

1.2 uC

= 1.2 uC

Energy

0.0000072 J

Capacitance, charge, voltage and energy

English capacitor intent usually combines the basic capacitance relationship with stored charge, stored energy and practical unit conversions from F, uF, nF and pF.

Q = C V

Q is charge, C capacitance and V voltage.

E = \frac{1}{2} C V^{2}

E is stored energy in joules.

Series, parallel and RC timing

C_{p a r a l l e l} = C_{1} + C_{2} + \dots + C_{n}

Parallel capacitors add directly.

\frac{1}{C _{ser i es}} = \frac{1}{C _{1}} + \frac{1}{C _{2}} + \dots + \frac{1}{C _{n}}

Series capacitors add by reciprocal capacitance.

τ = R C

tau is the first-order RC time constant.

Capacitor safety

Capacitors can retain dangerous voltage after power is removed. Discharge through an appropriate resistor and verify with a meter before handling.

Frequently Asked Questions

Sources and References

Calculations are based on the listed reference sources. Links open in a new tab.

Updated: June 2, 2026

Related Tools

RC Circuit Calculator

Calculate RC time constant, capacitor charge/discharge voltage, cutoff frequency, impedance and simple low-pass or high-pass filter behavior.

Open

Ohm's Law Calculator

Calculate voltage, current, resistance or power from any two known electrical values.

Open

Resistor Calculator

Calculate equivalent resistance for series or parallel resistors, estimate current and power, and decode resistor color bands or SMD markings.

Open

Electrical Power Calculator

Calculate DC, single-phase AC and three-phase AC electrical power, apparent power, reactive power and power factor correction.

Open

Voltage Drop Calculator

Estimate voltage drop, percent drop, conductor loss and recommended wire size for DC, single-phase and three-phase circuits.

Open