Capacitor Energy Calculator
Calculate the energy stored and charge in a capacitor
Microfarads (µF)
Volts (V)
How to Use This Calculator
Enter Capacitance
Enter the capacitor value in microfarads (µF). This is the capacitance rating of your capacitor.
Enter Voltage
Enter the voltage across the capacitor in volts. This can be the charging voltage or the voltage rating of the capacitor.
Calculate Results
Click calculate to see the stored energy in joules (J) or millijoules (mJ), and the stored charge in coulombs (C), millicoulombs (mC), or microcoulombs (µC).
Formula
E = ½ × C × V²
Q = C × V
Where:
- E = Energy stored (Joules)
- C = Capacitance (Farads)
- V = Voltage (Volts)
- Q = Charge stored (Coulombs)
Key Points:
- Energy is proportional to the square of voltage - doubling voltage quadruples energy
- Energy is proportional to capacitance - doubling capacitance doubles energy
- Charge is proportional to both capacitance and voltage
- Higher voltage capacitors store significantly more energy
Example 1:
Capacitance = 1000 µF, Voltage = 25 V
C = 1000 × 10-6 = 0.001 F
E = ½ × 0.001 × 25² = 0.5 × 0.001 × 625 = 0.3125 J (312.5 mJ)
Q = 0.001 × 25 = 0.025 C (25 mC)
Example 2:
Capacitance = 470 µF, Voltage = 16 V
E = ½ × (470 × 10-6) × 16² = 0.5 × 0.00047 × 256 = 0.06016 J (60.16 mJ)
Q = 0.00047 × 16 = 0.00752 C (7.52 mC)
About Capacitor Energy Calculator
The Capacitor Energy Calculator is a free online tool that helps you calculate the energy stored in a capacitor and the electric charge it holds. Understanding capacitor energy is crucial for power supply design, energy storage systems, defibrillators, flash photography, and many other applications where capacitors are used to store and release energy quickly.
When to Use This Calculator
- Power Supply Design: Calculate energy storage capacity for smoothing and filtering
- Energy Storage Systems: Design capacitor banks for energy storage applications
- Pulse Power: Determine capacitor size for high-power pulse applications
- Capacitor Selection: Choose appropriate capacitors based on energy requirements
- Educational Purposes: Learn about energy storage in capacitors
Why Use Our Calculator?
- ✅ Accurate Calculations: Uses the correct energy and charge formulas
- ✅ Multiple Units: Displays results in appropriate units (J/mJ, C/mC/µC)
- ✅ Easy to Use: Simple interface requiring only capacitance and voltage
- ✅ Dual Output: Calculates both energy and charge simultaneously
- ✅ Free Tool: No registration or payment required
- ✅ Educational: Includes formulas and examples for learning
Common Applications
Power Supply Filtering: Large capacitors in power supplies store energy to smooth voltage ripple. A 1000 µF, 25V capacitor stores 312.5 mJ of energy, which helps maintain stable voltage during load variations.
Flash Photography: Camera flash units use capacitors to store energy quickly and release it instantly as a bright flash. A typical flash capacitor might store 5-10 J of energy at high voltage (300-400V).
Defibrillators: Medical defibrillators use large capacitors to store energy (typically 100-360 J) that is discharged in a controlled pulse to restore heart rhythm.
Pulse Power Systems: High-energy pulse applications like laser drivers, particle accelerators, and railguns use capacitor banks to store and quickly release massive amounts of energy.
Tips for Accurate Results
- Enter capacitance in microfarads (µF) - the calculator converts to farads internally
- Energy is proportional to voltage squared - small voltage increases have large energy effects
- Ensure capacitor voltage rating exceeds the applied voltage to prevent damage
- Consider capacitor tolerance - actual energy may vary by ±5-20%
- For pulsed applications, ensure capacitor can handle the discharge current
- Energy is stored in the electric field, not in the capacitor material itself
Frequently Asked Questions
Why is energy proportional to voltage squared?
Energy stored in a capacitor comes from the work done to charge it. As voltage increases, more work is needed to move charges against the increasing electric field. The relationship E = ½CV² shows that doubling voltage quadruples energy because both the charge (Q = CV) and voltage increase.
Can a capacitor store infinite energy?
No, capacitors have maximum voltage ratings. Exceeding the rated voltage can cause dielectric breakdown and capacitor failure. The maximum energy is limited by both capacitance and voltage rating: E_max = ½C × V_rated².
How does energy compare to batteries?
Capacitors store much less energy per unit volume than batteries. However, capacitors can charge and discharge much faster (milliseconds) compared to batteries (hours). This makes capacitors ideal for applications requiring quick energy bursts.
What happens to the energy when a capacitor discharges?
When a capacitor discharges, the stored energy is released as current through the discharge path. It can power a load (like a flash bulb), be converted to heat (in a resistor), or be transferred to another capacitor. Energy is conserved but may be converted to different forms.
Can I calculate energy for capacitors in series or parallel?
For capacitors in parallel, total energy is the sum of individual energies. For capacitors in series, calculate total capacitance first (1/Ctotal = 1/C1 + 1/C2...), then use the same formula with total capacitance and the voltage across the series combination.