What is a capacitance calculator?

A capacitance calculator computes capacitance for various capacitor configurations: parallel-plate from physical dimensions, series and parallel combinations of multiple capacitors, RC time constants for charging/discharging circuits, and energy stored in a charged capacitor.

How do you calculate parallel-plate capacitance?

C = ε₀ × εᵣ × A / d, where ε₀ is the permittivity of free space (8.854×10⁻¹² F/m), εᵣ is the dielectric constant, A is the plate area in m², and d is the plate separation in meters. Larger area and smaller gap give larger capacitance.

How do capacitors combine in series?

Series: 1/C_total = 1/C₁ + 1/C₂ + 1/C₃. The total capacitance is always less than the smallest individual capacitor. Two equal capacitors in series produce half the capacitance. This is the opposite of how resistors combine in series.

How do capacitors combine in parallel?

Parallel: C_total = C₁ + C₂ + C₃. Capacitances add directly, just like resistors add in series. This is the easy way to get a larger capacitance from smaller capacitors. Voltage rating stays the same as the lowest individual capacitor.

What is the RC time constant?

The RC time constant τ = R × C measures how quickly a capacitor charges or discharges through a resistor. After 1τ the capacitor reaches 63% of its final voltage; after 5τ it reaches 99% (essentially fully charged). It's central to filter, timing, and oscillator design.

How much energy does a capacitor store?

E = ½ × C × V², in joules. A 1 mF capacitor at 12 V stores ½ × 0.001 × 144 = 0.072 J. Doubling the voltage quadruples the stored energy. This is why high-voltage capacitors can be dangerous even at modest capacitance values.

What is a dielectric and why does it matter?

A dielectric is the insulating material between capacitor plates. Its relative permittivity (εᵣ) multiplies the capacitance — vacuum is 1, air is ~1, glass is 5, water is 80, ceramics can reach 1000+. Higher εᵣ allows much higher capacitance in the same physical volume.

What are common capacitance units?

Farad (F) is the SI unit, but it's huge — most real capacitors are measured in microfarads (1 µF = 10⁻⁶ F), nanofarads (1 nF = 10⁻⁹ F), or picofarads (1 pF = 10⁻¹² F). Our calculator returns all four units so you can match any datasheet notation.

Capacitance Calculator

Capacitors are everywhere in electronics — power supplies, filters, timing circuits, energy storage. Our capacitance calculator handles the five most common capacitor calculations in one tool: parallel-plate capacitance from physical dimensions, series capacitor combinations (1/C = Σ1/Cᵢ), parallel combinations (C = ΣCᵢ), RC time constants (τ = R × C), and stored energy (E = ½CV²). Each mode uses the appropriate physics and reports results in all four common capacitance units (F, µF, nF, pF) so you can match whatever notation your circuit diagram or datasheet uses.

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calendar_today Updated: April 2026

auto_awesome AI Insights AI

New

bolt Capacitor Inputs

Calculation Mode

Area (m²)

Distance (m)

εᵣ

analytics Result

Capacitance

88.5 pF

8.85e-11

µF

0.089

88.542

Interpretation

Parallel-plate capacitance from area, separation, and dielectric constant

Input Values

Calculation Mode

Parallel Plate (from dimensions)

Series Combination

Parallel Combination

RC Time Constant

Stored Energy

Plate Area (m²)

Plate Separation (m)

Dielectric Constant (εᵣ)

C₁ (F)

C₂ (F)

C₃ (F, optional)

Resistance (Ω)

Capacitance (F)

Voltage (V)

tips_and_updates Tips

• Series capacitors: total capacitance is always LESS than the smallest individual capacitor
• Parallel capacitors: total capacitance is the SUM of all individual capacitors
• RC time constant τ = R × C — voltage reaches 63% of final in 1τ, 99% in 5τ
• Stored energy E = ½CV² scales with voltage² — doubling V quadruples energy
• Common dielectric constants: vacuum 1, air 1.0006, glass ~5, water 80, ceramic 10-3000
• Capacitors in series increase voltage rating; in parallel they increase capacitance
• Electrolytic capacitors are polarized — connect them backwards and they fail catastrophically

functions Formula

{C = ε₀εᵣA/d • Series: 1/C = Σ1/Cᵢ • Parallel: C = ΣCᵢ • τ = RC • E = ½CV² [{C Capacitance in farads (F)} {ε₀ Permittivity of free space = 8.854×10⁻¹² F/m} {εᵣ Relative permittivity (dielectric constant)} {A Plate area (m²)} {d Plate separation (m)} {τ RC time constant (seconds)} {5τ Time to fully charge/discharge (~99%)} {E Energy stored in joules} {Q Charge stored in coulombs}] A parallel-plate capacitor's capacitance is proportional to plate area and dielectric constant, inversely proportional to plate separation. Capacitors in series combine like resistors in parallel (the total is less than the smallest); capacitors in parallel combine additively. The RC time constant tells you how fast a capacitor charges or discharges through a resistor — voltage reaches 63% in 1τ and 99% in 5τ. Stored energy scales with the square of voltage.}

science Example: Parallel-plate capacitor, 1 cm² area, 1 mm gap, vacuum

C = (8.854×10⁻¹²) × 1 × 0.01 / 0.001 = 8.854×10⁻¹¹ F = 88.5 pF. This is a tiny capacitor — typical real-world capacitors achieve much higher capacitance by stacking many plates and using high-εr dielectrics like ceramic or electrolyte.

Expected Results

nF 0.1

pF 88.5

How to Use This Calculator

Select mode

Choose parallel plate, series, parallel, RC time, or energy.

Enter relevant inputs

Each mode uses different inputs — fill the ones for your selected mode.

Read result

See capacitance in F, µF, nF, pF plus mode-specific outputs.

The Formula

A parallel-plate capacitor's capacitance is proportional to plate area and dielectric constant, inversely proportional to plate separation. Capacitors in series combine like resistors in parallel (the total is less than the smallest); capacitors in parallel combine additively. The RC time constant tells you how fast a capacitor charges or discharges through a resistor — voltage reaches 63% in 1τ and 99% in 5τ. Stored energy scales with the square of voltage.

C = ε₀εᵣA/d • Series: 1/C = Σ1/Cᵢ • Parallel: C = ΣCᵢ • τ = RC • E = ½CV²

lightbulb Variables Explained

C Capacitance in farads (F)
ε₀ Permittivity of free space = 8.854×10⁻¹² F/m
εᵣ Relative permittivity (dielectric constant)
A Plate area (m²)
d Plate separation (m)
τ RC time constant (seconds)
5τ Time to fully charge/discharge (~99%)
E Energy stored in joules
Q Charge stored in coulombs

tips_and_updates Pro Tips

Series capacitors: total capacitance is always LESS than the smallest individual capacitor

Parallel capacitors: total capacitance is the SUM of all individual capacitors

RC time constant τ = R × C — voltage reaches 63% of final in 1τ, 99% in 5τ

Stored energy E = ½CV² scales with voltage² — doubling V quadruples energy

Common dielectric constants: vacuum 1, air 1.0006, glass ~5, water 80, ceramic 10-3000

Capacitors in series increase voltage rating; in parallel they increase capacitance

Electrolytic capacitors are polarized — connect them backwards and they fail catastrophically

Capacitors store electrical energy in an electric field between two conductors. They're used everywhere — smoothing power supply ripple, coupling AC signals between stages, blocking DC, setting timing in oscillators and filters, providing burst energy for camera flashes and motor starting. Understanding capacitance lets you size capacitors correctly for any of these applications without trial and error.

One thing that trips up new electronics engineers: capacitors combine the OPPOSITE way from resistors. Resistors in series add; capacitors in series combine like resistors in parallel (smaller). Resistors in parallel combine like 1/(1/R₁+1/R₂); capacitors in parallel just add. If you ever forget, remember that series capacitors are 'pulled apart' by the geometry, reducing effective capacitance, while parallel capacitors stack effective area, increasing it.

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