Capacitance Charge Calculator
Use this tool to calculate electric charge with the capacitor equation Q = C × V.
What this capacitance charge calculator does
A capacitor stores electric charge when a voltage is applied across its terminals. This calculator helps you quickly find that stored charge using the standard capacitor formula:
Where:
- Q = charge in coulombs (C)
- C = capacitance in farads (F)
- V = voltage in volts (V)
Because real-world work often uses microfarads, nanofarads, millivolts, or kilovolts, this calculator includes unit conversion automatically.
How to use the calculator
Step 1: Enter capacitance
Type your capacitor value and select the correct unit (F, mF, µF, nF, or pF).
Step 2: Enter voltage
Type the applied voltage and select unit (V, mV, or kV).
Step 3: Choose output unit
Select the charge unit you want for your final answer (C, mC, µC, nC, or pC).
Step 4: Calculate
Click Calculate Charge. The tool returns the charge and also shows stored energy using:
Worked examples
Example 1: Common electronics capacitor
If C = 100 µF and V = 5 V:
- Convert 100 µF = 100 × 10-6 F = 0.0001 F
- Q = C × V = 0.0001 × 5 = 0.0005 C
- Q = 500 µC
Example 2: High-voltage application
If C = 2 nF and V = 3 kV:
- 2 nF = 2 × 10-9 F
- 3 kV = 3000 V
- Q = 2 × 10-9 × 3000 = 6 × 10-6 C
- Q = 6 µC
Unit reference table
| Quantity | Unit | SI Conversion |
|---|---|---|
| Capacitance | 1 mF | 1 × 10-3 F |
| Capacitance | 1 µF | 1 × 10-6 F |
| Capacitance | 1 nF | 1 × 10-9 F |
| Charge | 1 mC | 1 × 10-3 C |
| Charge | 1 µC | 1 × 10-6 C |
| Voltage | 1 kV | 1000 V |
Common mistakes to avoid
- Skipping unit conversion: this is the #1 reason answers are off by powers of ten.
- Using wrong symbol: capacitance uses C, but charge also often uses Q to avoid confusion.
- Ignoring sign: negative voltage can produce negative charge depending on reference direction.
- Forgetting voltage limits: capacitor ratings must not be exceeded, even if your math is correct.
Where this is useful
- RC timing circuits
- Power supply smoothing
- Sensor and analog front-end design
- Educational physics and electronics labs
- Quick field calculations during troubleshooting
Quick FAQ
Can charge be negative?
Yes. The sign depends on polarity and how you define the reference direction.
What if voltage is zero?
Then Q = 0. No potential difference means no stored charge in the ideal capacitor model.
Does this include leakage or ESR?
No. This is an ideal capacitor equation calculator. Leakage current, ESR, and dielectric effects are not modeled.