Capacitor Size Calculator
Estimate AC capacitance from current, frequency and voltage.
Interactive Electrical Calculator
Capacitor Size Calculator
Estimate AC capacitance from current, frequency and voltage.
Result
Enter values and calculate.
About the Capacitor Size Calculator
Use the Capacitor Size Calculator below to work through component-level calculations for resistors, capacitors and basic AC circuit behavior in seconds, right in your browser. Estimate AC capacitance from current, frequency and voltage. Reactance, resonance and time-constant calculations explain why a circuit behaves differently at different frequencies, which pure DC thinking does not capture.
It's built for electronics hobbyists, students and engineers designing or troubleshooting small circuits, and every field updates instantly so you can try a few scenarios before committing to a real installation.
How the calculation works
Here is the relationship the calculator solves for you:
C = I / (2πfV).
Where each input maps to a field in the calculator above:
- Capacitor Current in A.
- Frequency in Hz.
- Voltage in V.
Every one of these values can be edited above, and the calculator updates the result the moment you press Calculate.
Important: This simplified relation is for ideal capacitive current.
A worked example
For example, start with 5 A for capacitor current, 50 Hz for frequency and 230 V for voltage. Those defaults are only a starting point — replace them with your own measured or nameplate values, then press Calculate to get a result specific to your situation.
When to use the Capacitor Size Calculator
Typical reasons people reach for the Capacitor Size Calculator:
- Picking a resistor or capacitor value for a specific circuit target.
- Checking a component combination before ordering parts or building a prototype.
- Working out a circuit's behavior at a specific frequency.
- Verifying a calculated value against a datasheet or standard component range.
Good practice: Component tolerances (typically 1-10% for resistors, wider for capacitors) mean a calculated value is a target, not a guarantee — pick the nearest standard value and check the result still meets your requirement.
Also worth knowing: Reactance is frequency-dependent, so a capacitor or inductor calculation is only valid at the specific frequency it was calculated for.
Frequently asked questions
What does the Capacitor Size Calculator calculate?
Estimate AC capacitance from current, frequency and voltage.
Is the result exact enough to build from?
The formula above is applied exactly to the values you enter, so the math itself is precise. Real-world results can still differ due to component tolerances, temperature, installation method, equipment efficiency and local code requirements, so treat the output as a strong planning estimate and verify final designs against manufacturer data and the electrical code that applies to your installation.
Does this calculator store or send my data anywhere?
No. The Capacitor Size Calculator runs entirely in your browser, and nothing you type is transmitted or stored anywhere.
Why does this calculation matter in practice?
Reactance, resonance and time-constant calculations explain why a circuit behaves differently at different frequencies, which pure DC thinking does not capture.
Can I use this on a phone, or does it need a desktop?
The Capacitor Size Calculator works on any modern browser, phone or desktop, and recalculates as soon as you press Calculate. If a result looks off, double-check that every field is filled in with the unit shown next to it (mixing up units, such as W with kW, is the most common cause of an unexpected answer) and re-enter the values.