Capacitors in Series & ParallelCalculator
Calculate total capacitance and safe maximum voltage for capacitor banks. Switch between series and parallel modes to understand circuit behavior.
Capacitor Bank Calculator
Configure components and view results
Circuit Components
Total Capacitance
C = ΣCₙ
Max Safe Voltage
Limited by lowest voltage rating
Energy at max voltage
25.60 mJ
Parallel Connection
Connecting capacitors in parallel is the easiest way to increase total capacitance. Think of it as combining the plate surface area.
Voltage Rule
All capacitors share the same voltage. The maximum safe voltage equals the lowest rated capacitor.
Series Connection
Series connections increase total voltage rating at the cost of reduced capacitance. Useful for high-voltage applications.
Voltage Rule
Voltage divides inversely to capacitance. Smaller capacitors see higher voltage—use the charge balance method (Q = CV).
Important Safety Information
Series Voltage Division
In real circuits, leakage current varies between capacitors, causing uneven voltage distribution. Without balancing resistors, some capacitors may exceed their voltage rating.
Recommended Practice
Always use balancing resistors (typically 100kΩ-1MΩ) across each capacitor in series. Alternatively, de-rate the maximum voltage by 20-30% for safety margin.
Quick Reference Formulas
Parallel Capacitance
C = C₁ + C₂Series Capacitance
1/C = 1/C₁ + 1/C₂Charge (Series)
Q = Q₁ = Q₂Energy Stored
E = ½CV²Common Capacitor Combinations
Total capacitance for the pairings that come up most often, worked from C = C₁ + C₂ in parallel and 1/C = 1/C₁ + 1/C₂ in series.
| Capacitors | In Parallel | In Series |
|---|---|---|
| 2 x 10 µF | 20 µF | 5 µF |
| 2 x 47 µF | 94 µF | 23.5 µF |
| 2 x 100 µF | 200 µF | 50 µF |
| 2 x 470 µF | 940 µF | 235 µF |
| 3 x 100 µF | 300 µF | 33.3 µF |
| 100 µF + 47 µF | 147 µF | 32.0 µF |
| 100 µF + 10 µF | 110 µF | 9.09 µF |
| 1 µF + 0.1 µF | 1.1 µF | 0.0909 µF |
Parallel banks are limited by the lowest voltage rating present. Series strings add voltage rating only when the capacitors are matched and balanced — see the safety note above.
Frequently Asked Questions
How do you calculate capacitors in parallel?
Capacitance in parallel simply adds: C_total = C1 + C2 + ... + Cn. A 100 µF capacitor in parallel with a 47 µF capacitor gives 147 µF. The voltage rating does not add — the bank is limited by the lowest-rated capacitor in the group.
How do you calculate capacitors in series?
Series capacitance follows the reciprocal rule: 1/C_total = 1/C1 + 1/C2 + ... + 1/Cn. For exactly two capacitors there is a shortcut: C_total = (C1 x C2) / (C1 + C2). So 100 µF in series with 47 µF gives (100 x 47) / 147 = 32.0 µF. Two identical capacitors in series always give half the value of one.
Why does total capacitance decrease when capacitors are in series?
Every capacitor in a series string carries the same charge Q, but the supply voltage divides across all of them. Since C = Q/V, holding the charge constant while increasing the total voltage means the effective capacitance falls. It is the mirror image of resistors, where series resistance adds.
What voltage rating do I need for capacitors in series?
In theory the ratings add, so two 250 V capacitors in series withstand 500 V. In practice voltage divides inversely to capacitance, so the smallest capacitor in the string sees the highest voltage, and differences in leakage current make the split uneven over time. Use capacitors of matched value and tolerance, fit balancing resistors (typically 100 kΩ to 1 MΩ) across each one, or derate the calculated maximum by 20 to 30 percent.
Do capacitors in parallel increase the voltage rating?
No. Parallel capacitors all see the full supply voltage, so the safe maximum is the voltage rating of the lowest-rated capacitor in the bank — not the sum, and not the average. Mixing a 450 V and a 100 V capacitor in parallel gives you a 100 V bank.
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