Capacitance Calculator

Compute capacitance from charge/voltage or geometry, calculate equivalent capacitance for series/parallel networks, determine RC time constants, and estimate dielectric breakdown voltage.

?️ Air: A=1e-4 m², d=1 mm ? Ceramic: A=2e-4 m², d=0.2 mm, εᵣ=1200 ? Basic: Q=10 µC, V=12 V ⚙️ Electrolytic: A=0.01 m², d=50 µm, εᵣ=25
Privacy first: All calculations run locally in your browser – no data transmitted.

? Series & Parallel Capacitor Networks

Calculate equivalent capacitance (Ceq) for up to three capacitors connected in series or parallel. Useful for filter design, timing circuits, and power supply smoothing.

Formulas: Parallel: Ceq = C₁ + C₂ + C₃ ; Series: 1/Ceq = 1/C₁ + 1/C₂ + 1/C₃.

⏱️ RC Time Constant & Cutoff Frequency

The RC time constant τ = R·C defines charge/discharge rate and the cutoff frequency fc = 1/(2πRC) for low‑pass/high‑pass filters.

Engineering Practice Tips

Safety Margin: In practical design, operating voltage should be less than 50% of breakdown voltage (2× safety factor). Further derating is required in high-temperature environments.

Capacitor Parallel Connection: When multiple capacitors are connected in parallel, total ESR reduces but watch for resonance peaks. Large electrolytic capacitors are often paralleled with 0.1µF ceramic capacitors to reduce high-frequency impedance.

⚡ Dielectric Breakdown Voltage Estimator

Estimate the maximum voltage a capacitor can withstand before dielectric breakdown, using material dielectric strength (from table below) and thickness.

Capacitor Type Selection Quick Reference

Application Recommended Capacitor Type Typical Range Key Considerations
High-frequency decoupling (IC power pins) MLCC (X7R/X5R ceramic) 0.01µF - 0.1µF Low ESL, place close to power pins
Power input filtering Aluminum electrolytic/Polymer 10µF - 1000µF Check rated voltage and ripple current
RC timing circuits Film (polyester, polypropylene) 1nF - 1µF Low leakage, good temperature stability
Audio coupling Non-polarized electrolytic/Film 1µF - 10µF Low distortion, calculate cutoff frequency
About This Tool

Development Team: This tool is developed and maintained by the GetZenQuery engineering team. We specialize in creating accurate, practical scientific calculation tools for engineers, students, and hobbyists worldwide.

Quality Assurance: All formulas are based on standard physics textbooks, and calculations undergo multiple cross-verification rounds. The tool's code is open for review, and we welcome feedback.

Fundamentals of Capacitance & Practical Design

Capacitance is defined as C = Q/V. For parallel‑plate capacitors, C = ε₀·εᵣ·(A/d). The farad (F) is the SI unit, named after Michael Faraday. Modern electronics use capacitors ranging from picofarads (pF) to kilofarads (supercapacitors).

Real‑World Example: Decoupling Capacitor Selection
For a digital IC drawing 100 mA with a maximum allowable ripple of 50 mV at 10 MHz, the required capacitance C = I / (f·V_ripple) = 0.1 / (10e6·0.05) = 0.2 µF. Our series/parallel calculator helps combine standard values (e.g., 0.1 µF + 0.1 µF parallel = 0.2 µF).

Dielectric Material Properties (Expanded)

Material εᵣ (relative permittivity) Dielectric strength (MV/m) Typical application
Air 1.0006 3 Variable capacitors, high‑voltage
Polyester (Mylar) 3.3 200 General purpose film caps
Ceramic X7R 2000–4000 10 Decoupling, temperature‑stable
Tantalum 25 600 High‑density, low‑ESR
Aluminum electrolytic 8–10 500 Power supply smoothing

RC Time Constant in Practice

In an RC circuit, the time constant τ = R·C determines how quickly a capacitor charges to 63.2% of the supply voltage. For timing applications (e.g., 555 timer), the frequency is approximately 1/(1.1·R·C). Our calculator also gives the cutoff frequency fc = 1/(2πRC) for passive filters.

Industrial Application: Power Supply Filter Design

A full‑bridge rectifier produces 120 Hz ripple. For a load of 2 A and desired ripple of 0.5 V, the required filter capacitance C = I / (f·V_ripple) = 2 / (120·0.5) ≈ 33,333 µF. Using our series/parallel calculator, you can combine three 10,000 µF capacitors in parallel to achieve 30,000 µF, or two 15,000 µF units.

Frequently Asked Questions

1 µF = 1000 nF = 1,000,000 pF. Our series/parallel calculator accepts suffixes like "10µF" or "22nF" for convenience.

Because the effective plate separation increases, reducing the equivalent capacitance. The voltage divides across each capacitor.

Use 0.1 µF ceramic capacitors near each IC power pin, plus a larger 10–100 µF electrolytic near the power input.

Based on industry design guidelines (e.g., TI, ADI application notes):

  • Input capacitors: Handle high-frequency current ripple. Ceramic capacitors (0.1-10µF) near IC pins, electrolytic/polymer capacitors (10-100µF) for low-frequency ripple.
  • Output capacitors: Determine load transient response. Use our RC calculator to determine capacitance for target ripple voltage: C ≥ ΔI/(8·f·ΔV), where ΔI is load step, f is switching frequency.
  • Practical considerations: Check capacitor ESR (Equivalent Series Resistance) and rated ripple current, both frequency-dependent.

Reference: Texas Instruments "Switching Power Supply Design Guide" Chapter 3, Analog Devices "Power Management Fundamentals".

Electrolytic capacitors (aluminum, tantalum) use an oxide layer as dielectric, requiring correct polarity for formation:

  • Polarity principle: Anode aluminum foil forms Al₂O₃ insulating layer (~1.4nm/V) through electrochemical process. Reverse voltage destroys this oxide layer.
  • Reversal consequence: Rapid gas generation causes capacitor swelling, leakage, and eventual short circuit or explosion. Our breakdown voltage calculator doesn't apply to this nonlinear case.
  • Non-polar electrolytics: Essentially two polarized capacitors in reverse series, with halved capacitance and increased size.

Warning: Electrolytic capacitor reversal is a common failure mode – pay attention to PCB polarity markings.

Authoritative References & Verification Sources:

  • Fundamental Constants: Vacuum permittivity ε₀ = 8.854187817×10⁻¹² F/m from NIST CODATA 2022 values
  • Capacitance Formulas: Parallel-plate formula C = ε₀εᵣA/d from Halliday & Resnick "Fundamentals of Physics" 10th Ed. Chapter 25
  • Dielectric Strength Data: References IEEE Std 1-2000 "Dielectric Strength Test Standard" and manufacturer technical documents (Kemet, TDK)
  • Engineering Practice: Switching power supply capacitor selection references Texas Instruments "AN-1149 Application Note"

Transparency Statement: This tool's core calculation code is open for inspection via browser developer tools. All computations run locally with no data transmission. We welcome peer review and technical feedback.