What is the RC time constant?

τ = R × C (resistance times capacitance). After one time constant, a capacitor charges to 63.2% of supply voltage. After 5τ it is considered fully charged (99.3%).

What is the difference between series and parallel capacitors?

Capacitors in parallel add their capacitances (Ctotal = C1 + C2 + ...). In series, reciprocals add (1/Ctotal = 1/C1 + 1/C2 + ...) resulting in a smaller total capacitance.

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Capacitor Calculator

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Voltage

Q = C × VE = ½CV²V = Q / C

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Three modes: charge/energy (Q=CV, E=0.5CV2), RC charging/discharging (time constant, voltage at time t), series and parallel capacitor combinations up to 5 caps.

How to Use

1Select a tab: Charge & Energy, RC Charging/Discharging, or Series/Parallel
2Charge tab: enter any two of charge Q, capacitance C, or voltage V - the third is solved
3RC tab: enter resistance, capacitance, and supply voltage to get τ = RC and voltage at any time t
4Series/Parallel: add up to 5 capacitor values - total capacitance is calculated
5Select appropriate unit prefixes (pF, nF, μF, mF, F) for each capacitor

Features

3 modes: Charge/Energy, RC Charging/Discharging, Series/Parallel
Solves Q=CV and E=½CV² for any unknown
RC time constant τ=RC with voltage at any time t
Charging and discharging curves
Up to 5 capacitors in series or parallel
Full SI prefix support (pF to F)
100% browser-based

Capacitor Calculator

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