Calculator
Example Data Table
| Capacitor | Value | Unit | Voltage | Equivalent C | Total Charge | Stored Energy |
|---|---|---|---|---|---|---|
| 3 capacitors in parallel | 10, 4.7, 100 | µF, µF, nF | 12 V | 14.8 µF | 177.6 µC | 1.066 mJ |
Formula Used
- Parallel capacitance: Ceq = C1 + C2 + … + Cn
- Total charge (optional): Q = Ceq · V
- Stored energy (optional): E = ½ · Ceq · V²
How to Use This Calculator
- Enter each capacitor value and select its unit.
- Use “Add Capacitor” to include more branches.
- Pick your preferred output unit for the result.
- Optionally enter voltage to compute charge and energy.
- Optionally add tolerance to view a min–max range.
- Press Calculate to see results above the form.
- Use the CSV or PDF buttons to export results.
Parallel Capacitors Explained
1) Why parallel capacitors matter
Parallel capacitors are used when you need more total capacitance, lower impedance, or better transient response. In power rails, adding small ceramics beside a larger electrolytic helps cover both fast spikes and slower load steps. In parallel, capacitances add linearly while voltage stays the same, so the network stores more charge at a given supply voltage. This calculator models the “same voltage, added storage” behavior.
2) Core rule and quick check
For parallel networks, the equivalent capacitance is the sum: Ceq = C1 + C2 + … + Cn. If you have n identical capacitors, the shortcut is Ceq = n·C. A quick check is that Ceq must be larger than the largest single capacitor. If it is smaller, a unit mistake is likely.
3) Unit conversions you will meet
Capacitance spans wide scales, so unit discipline matters. 1 mF = 10-3 F, 1 µF = 10-6 F, 1 nF = 10-9 F, and 1 pF = 10-12 F. Example: 100 nF equals 0.1 µF, so it adds cleanly to µF values.
4) Typical capacitor values and uses
Common decoupling capacitors sit around 10 nF to 1 µF near IC pins, while bulk smoothing may use 10 µF to 4700 µF on supply rails. RF or timing networks often use pF to low nF. Mixing types is normal, but always confirm voltage rating and polarity for electrolytics.
5) Charge and energy at working voltage
When you enter voltage, the calculator estimates total charge Q = Ceq·V and stored energy E = ½·Ceq·V². For the example set (10 µF, 4.7 µF, 100 nF), Ceq ≈ 14.8 µF. At 12 V, Q ≈ 177.6 µC and E ≈ 1.066 mJ.
6) Tolerance and real world spread
Capacitors rarely equal their label. Ceramics can be ±10% or ±20%, and effective capacitance may drop under DC bias. Use the tolerance input to view a simple min–max envelope around the total. This is useful when sizing hold-up time or filtering margins.
7) Practical wiring tips and mistakes
Parallel capacitors work best with short, wide traces and a solid return path. Series inductance can dominate at high frequency, so smaller capacitors placed closer to the load often outperform a single large part. For high currents, place the bulk capacitor near the power entry and the small ceramics at the switching load. Double-check units, polarity, and voltage rating before building.
FAQs
1) What is the equivalent capacitance in parallel?
The equivalent capacitance is the sum of all branch capacitances: Ceq = C1 + C2 + … + Cn. All capacitors share the same voltage in a parallel connection.
2) Why does my total look wrong?
Most errors come from mixed units. For example, 100 nF is 0.1 µF, not 100 µF. Ensure each value uses the correct unit, and confirm all inputs are positive numbers.
3) Can I mix electrolytic and ceramic capacitors?
Yes. Designers often combine a bulk electrolytic (µF to mF) with small ceramics (nF to µF) for better frequency coverage. Always check voltage rating, temperature rating, and polarity for electrolytics.
4) What does the voltage option calculate?
It estimates total charge and stored energy using Q = Ceq·V and E = ½·Ceq·V². These values help compare storage across designs and validate expected hold-up behavior.
5) How should I use tolerance results?
Tolerance gives a quick min–max range around the total capacitance. Use it for margin checks, especially when parts are ±10% or ±20%. Real circuits can vary more due to bias, aging, and temperature.
6) Does the calculator include ESR or inductance?
No. It focuses on ideal capacitance addition. For high-frequency behavior, ESR and ESL affect impedance and resonance. Use this tool for sizing totals, then validate with datasheets or impedance plots for final design.