Series and Parallel Capacitor Calculator
Equivalent capacitance from a capacitor list
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Quick Answer
Capacitors in parallel ADD: C_total = C1 + C2 + ... Capacitors in series use the reciprocal formula: 1/C_total = 1/C1 + 1/C2 + ... This is the OPPOSITE of how resistors combine.
Series & Parallel Capacitor Calculator
Calculate the equivalent capacitance of capacitors connected in series or parallel.
Parallel Capacitors
Capacitors in parallel add directly:
Ctotal = C1 + C2 + C3 + ... + Cn
Series Capacitors
Capacitors in series use the reciprocal formula:
1/Ctotal = 1/C1 + 1/C2 + 1/C3 + ... + 1/Cn
For two capacitors: Ctotal = (C1 x C2) / (C1 + C2)
Note: This is the opposite of resistors -- capacitors in parallel add, in series they reduce.
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Design Notes
Capacitor networks are everywhere in electronics. Parallel combinations increase total capacitance and reduce ESR — essential for power supply decoupling where multiple small MLCCs outperform one large electrolytic. Series combinations increase voltage rating at the cost of capacitance. When mixing types in parallel (e.g., 100µF electrolytic + 100nF ceramic), each type handles a different frequency range, providing broadband filtering.
Common Mistakes
- 1
Confusing capacitor series/parallel rules with resistor rules — they are OPPOSITE. Capacitors in parallel add (like resistors in series).
- 2
Putting capacitors in series without balancing resistors. Without equalization, voltage distributes unevenly and one capacitor may exceed its voltage rating.
- 3
Using only large capacitors for decoupling. Large caps have high ESL and poor high-frequency response. Always add small MLCCs in parallel.
Engineering Handbox
1. Parallel: simply add all values 2. C_total = 10 + 22 + 47 = 79 µF 3. For series: 1/C = 1/10 + 1/22 + 1/47 = 0.1 + 0.0455 + 0.0213 = 0.1667 4. C_series = 1/0.1667 = 6.0 µF
Knowledge Base
How do capacitors behave in parallel?
Parallel capacitors add directly: C_total = C1 + C2 + ... + Cn. This is the OPPOSITE of resistors. Parallel capacitors increase total capacitance, increase total energy storage, and share the same voltage. The combined ESR decreases, improving high-frequency performance.
What is the formula for capacitors in series?
1/C_total = 1/C1 + 1/C2 + ... + 1/Cn. The total is always LESS than the smallest individual capacitor. For two capacitors: C_total = (C1 × C2) / (C1 + C2). This is the same product-over-sum formula used for parallel resistors. Series capacitors behave like parallel resistors and vice versa.
Why would I put capacitors in series?
To increase the voltage rating. Each capacitor only sees a fraction of the total voltage. Two 25V 100uF caps in series give 50uF at 50V. Also used in voltage multiplier circuits. Important: add equalizing resistors (100k-1M) across each capacitor to ensure even voltage sharing, especially with electrolytics.
Why would I put capacitors in parallel?
Three main reasons: (1) Increase total capacitance beyond what a single cap provides. (2) Reduce ESR/ESL for better high-frequency performance — common in power supply decoupling. (3) Combine different types (e.g., 10uF electrolytic + 100nF ceramic) to filter a wide frequency range.
Can I mix different capacitor types in parallel?
Yes, this is actually best practice for power supply decoupling. A typical combination: 100uF bulk electrolytic (low-frequency filtering) + 1uF X7R ceramic (mid-frequency) + 100nF C0G ceramic (high-frequency). Each type handles a different part of the frequency spectrum.
Do capacitors in series share voltage equally?
Only if they have identical capacitance AND leakage current. In practice, manufacturing tolerances and different leakage rates cause uneven voltage distribution. The capacitor with lower leakage ends up with higher voltage and may exceed its rating. Always add balancing resistors (100k-1M) in parallel with each series capacitor.
What is ESR and why does it matter for parallel capacitors?
ESR (Equivalent Series Resistance) is the internal resistance of a capacitor. Paralleling caps reduces total ESR: ESR_total = 1/(1/ESR1 + 1/ESR2 + ...). Lower ESR means less voltage ripple in power supplies and faster transient response. This is why multiple small MLCCs outperform one large electrolytic for decoupling.
How do I calculate energy stored in capacitor networks?
Energy in a single capacitor: E = ½CV². For series capacitors: use C_total and total voltage. For parallel capacitors: sum individual energies or use C_total and the shared voltage. Example: two 100uF caps at 10V in parallel = ½ × 200µF × 100 = 10 mJ. Same caps in series = ½ × 50µF × 400 = 10 mJ (each cap sees 10V, total is 20V).
What is the difference between capacitors and resistors in series/parallel?
They are mathematical OPPOSITES. Resistors in series ADD (like capacitors in parallel). Resistors in parallel use the reciprocal formula (like capacitors in series). This duality occurs because resistance opposes current flow while capacitance stores charge — fundamentally opposite behaviors.
How many decoupling capacitors do I need per IC?
General rule: at least one 100nF ceramic capacitor per power pin, placed as close to the pin as possible. For high-speed digital ICs (FPGAs, processors), add a 10uF bulk cap per power group plus 100nF per pin. For very high-speed (>1 GHz), add 1nF or smaller caps for resonance-free decoupling across the full spectrum.
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