Capacitance Calculator — Charge, Voltage, and Energy
Calculate capacitance, charge, voltage, and stored energy. Covers parallel plate formula, series/parallel combinations, and applications in circuits and electronics.
Capacitors store electric charge and energy in an electric field. Unlike batteries, they can charge and discharge almost instantaneously — which is why they're used for camera flashes, power supply filtering, and timing circuits. Understanding capacitance helps you design circuits that need to hold, release, or filter electrical energy.
The CalcHub capacitance calculator handles charge, voltage, energy, and series/parallel combinations.
Key Formulas
Basic relationship: Q = C × V Energy stored: E = ½ × C × V² Parallel plate capacitor: C = ε₀ × ε_r × A / d- C = capacitance (Farads, F)
- Q = charge (Coulombs, C)
- V = voltage (Volts, V)
- ε₀ = 8.85 × 10⁻¹² F/m (permittivity of free space)
- ε_r = relative permittivity of dielectric
- A = plate area (m²)
- d = plate separation (m)
Combining Capacitors
| Configuration | Formula |
|---|---|
| Parallel | C_total = C₁ + C₂ + C₃ + ... |
| Series | 1/C_total = 1/C₁ + 1/C₂ + 1/C₃ + ... |
Common Capacitance Values
| Component | Capacitance |
|---|---|
| Small ceramic capacitor | 1 pF – 10 nF |
| Electrolytic (power supply) | 10 μF – 10,000 μF |
| Supercapacitor | 1 F – 3000 F |
| Earth's capacitance | ~710 μF |
Worked Example
A 100 μF capacitor is charged to 12 V. How much energy is stored?
E = ½ × 100 × 10⁻⁶ × 12² = 0.5 × 100 × 10⁻⁶ × 144 = 7.2 × 10⁻³ J = 7.2 mJ
Small, but delivered almost instantly for a flash. A camera flash uses ~100–400 μF at 300 V: E = ½ × 200 × 10⁻⁶ × 90,000 = 9 J — enough to produce a bright flash in milliseconds.
What is a dielectric and why does it increase capacitance?
A dielectric is an insulating material placed between capacitor plates. Its molecules polarize in the electric field, effectively reducing the field strength inside, which allows more charge to accumulate at the same voltage. Higher ε_r = more charge per volt = more capacitance. Common dielectrics include ceramic (ε_r = 5–10,000), polyester (3.2), and electrolyte (very high, used in electrolytics).
Why do electrolytic capacitors have polarity?
Electrolytic capacitors use an oxide layer formed electrolytically as the dielectric. This layer forms correctly only with the right polarity applied. Reverse polarity damages the oxide layer and can cause failure — sometimes violently. Always check +/− markings on electrolytics.
What's a supercapacitor?
Also called ultracapacitors or EDLCs (electric double-layer capacitors). They store charge at the interface between electrode and electrolyte, achieving enormous capacitance (thousands of farads) in compact form. They sit between batteries and conventional capacitors: more energy than caps, faster discharge than batteries. Used in regenerative braking systems and backup power supplies.