Capacitor Calculator Inputs
Plotly Graph
The first graph shows reactance versus frequency for the calculated capacitance. The second graph shows stored energy versus voltage.
Example Data Table
| Case | Method | Inputs | Calculated Capacitance | Use Case |
|---|---|---|---|---|
| 1 | Charge and voltage | Q = 4.7 µC, V = 5 V | 0.94 µF | Sensor hold circuit |
| 2 | Energy and voltage | E = 2 mJ, V = 12 V | 27.78 µF | Pulse energy storage |
| 3 | RC time constant | R = 10 kΩ, τ = 0.22 s | 22 µF | Delay network |
| 4 | Reactance and frequency | f = 1 kHz, Xc = 33.86 Ω | 4.7 µF | AC coupling estimate |
| 5 | Ripple filter sizing | I = 0.2 A, f = 100 Hz, Vr = 2 V | 1000 µF | Rectifier smoothing |
Formula Used
1) Charge and Voltage Method
Use this when charge storage and operating voltage are known. It is common in sample-and-hold, timing, and measurement circuits.
2) Energy and Voltage Method
Use this when you know the energy requirement and the capacitor voltage. This is practical for pulse support and short-term storage design.
3) RC Time Constant Method
This method sizes capacitance from resistor value and desired delay. The time constant controls charge and discharge speed in RC networks.
4) Reactance and Frequency Method
Use this for AC analysis. Lower reactance at a given frequency means higher capacitance. It is useful for filters, coupling, and bypass decisions.
5) Ripple Filter Approximation
This approximation estimates the smoothing capacitor needed for a target ripple voltage, given load current and ripple frequency.
How to Use This Calculator
- Select the calculation mode that matches your known design values.
- Enter inputs using the most convenient engineering units.
- Press the calculate button to show the result above the form.
- Review capacitance, energy, charge, reactance, and timing outputs.
- Use the graphs to inspect frequency response and energy scaling.
- Export the current result as CSV or PDF for documentation.
- Compare the preferred standard value with available capacitor series.
- Validate voltage rating, tolerance, ESR, leakage, and temperature separately.
Frequently Asked Questions
1) What does this tool calculate?
It estimates capacitance using several engineering methods, including charge-voltage, energy-voltage, RC timing, reactance-frequency, ripple filtering, and combination comparison.
2) Why are there multiple calculation modes?
Different circuit problems start with different known values. This tool lets you solve capacitance from the quantities you already have instead of converting everything manually.
3) Does the tool pick a real standard capacitor?
It suggests a nearby E12 preferred value. That helps with part selection, but you should still verify voltage rating, tolerance, package, ESR, and availability.
4) Is the ripple filter formula exact?
No. It is a practical approximation for early sizing. Real ripple depends on rectifier topology, ESR, load variation, and mains frequency conditions.
5) Why does reactance drop at higher frequency?
Capacitive reactance is inversely proportional to frequency. As frequency rises, a capacitor offers less opposition to alternating current.
6) Can I use this for timing circuits?
Yes. The RC mode is useful for estimating capacitance from a desired time constant and resistor value in delay or filter networks.
7) Does this replace full circuit simulation?
No. It is best for design estimation and quick checks. Use simulation and datasheet review before finalizing a hardware design.
8) What extra factors should engineers check?
Check voltage derating, ESR, ESL, tolerance, dielectric class, leakage current, temperature behavior, lifespan, and surge conditions before selecting the final component.