Capacitor Calculator
Calculate energy storage, charge, RC time constants, and series/parallel capacitor combinations with multi-unit support.
How the Capacitor Calculator Works
Three modes to handle all common capacitor calculations.
Basic Q and E
Calculate charge Q = C × V and energy E = ½CV² in Joules and mWh from capacitance and voltage.
RC Circuit
Find the RC time constant τ = RC and use the charging curve V(t) = Vs × (1 − e−t/τ) with an interactive slider.
Series / Parallel
Add multiple capacitors with any units. Series: 1/Ctotal = Σ(1/Cn). Parallel: Ctotal = Σ(Cn).
Frequency Asked Questions
Common questions about capacitor calculations.
Energy stored is E = ½ × C × V². For example, a 1000 µF capacitor charged to 12V stores 0.5 × 0.001 × 144 = 0.072 Joules (72 mJ), which equals approximately 0.02 mWh. Use our calculator to enter any capacitance and voltage with auto unit conversion.
The RC time constant τ = R × C determines how fast a capacitor charges or discharges. After one time constant (t = τ), the voltage reaches 63.2% of the source. After five time constants (5τ), it reaches 99.3% and is considered fully charged. This is critical in filter design, timing circuits, and power supply smoothing.
For parallel capacitors, simply add all values: Ctotal = C&sub1; + C&sub2; + ... + Cn. For series capacitors, add the reciprocals: 1/Ctotal = 1/C&sub1; + 1/C&sub2; + ... + 1/Cn. Series capacitance is always less than the smallest capacitor in the chain.