What Is the Capacitor Calculator?

The Capacitor Calculator is an all-in-one tool for computing key capacitor parameters. Whether you're designing a power supply filter, selecting a coupling capacitor, or sizing a motor-run capacitor, this calculator gives you instant, accurate results.

Basic Calculator

Find capacitance (C), voltage (V), charge (Q), and stored energy (E) from any two known values

Impedance Calculator

Calculate capacitive reactance (Xc) at a given frequency, with an optional AC current result

Series & Parallel

Combine multiple capacitors to find total equivalent capacitance

Universal Unit Support: All calculations support SI unit prefixes (pF through F, mV through kV, Hz through MHz), so you can work directly with the values printed on your components.

How to Use

Basic Calculator

Select Mode

Click the Basic tab to access the fundamental capacitor calculations

Enter Values

Input any two of the three values: Capacitance (C), Voltage (V), or Charge (Q)

Choose Units

Select the correct unit for each value using the dropdown (pF, nF, µF, etc.)

Get Results

The calculator instantly computes the missing value plus the stored energy (E)

Smart Input: If you enter a third value, the oldest input is automatically cleared — no manual erasing needed.

Impedance Calculator

Select Mode

Click the Impedance tab to access AC circuit calculations

Enter Required Values

Input the capacitance (C) and frequency (f) — both values are required for impedance calculation

View Reactance

The capacitive reactance (Xc) is calculated using the formula Xc = 1/(2πfC)

Optional Current

Enter a voltage value to also see the AC current through the capacitor

Analyze Response

A frequency response chart shows how Xc varies across the frequency spectrum

Series & Parallel

Select Mode

Click the Series & Parallel tab to access combination calculations

Choose Configuration

Select Parallel or Series mode based on your circuit design

Enter Capacitor Values

Input capacitor values — you start with two and can add up to ten capacitors

View Total Capacitance

The total equivalent capacitance is calculated in real time as you type

Manage Capacitors: Use the trash icon to remove a capacitor (minimum two required for combination calculations).

General Tips

Adjust Precision to control the number of decimal places (2–6) for more accurate or simplified results
Click Examples to try common real-world circuit values and learn typical applications
Click Reset to clear all inputs in the current tab and start fresh

Quick Start: New to capacitor calculations? Start with the Examples button to see how different circuit types use capacitors in practice.

Features

Three Calculation Modes

Switch between Basic (Q, V, C, E), Impedance (Xc, AC current), and Series/Parallel combination modes with a single click.

Basic parameters calculation
AC impedance analysis
Capacitor combinations

Smart Input Tracking

In Basic mode, enter any two values and the third is computed automatically. If you enter a third value, the oldest one is cleared — no need to manually erase fields.

Automatic field management
Instant calculations
Intuitive workflow

Full SI Prefix Support

Select from picofarads to farads, millivolts to kilovolts, and hertz to megahertz. Results are auto-scaled to the most readable prefix.

pF to F capacitance range
mV to kV voltage range
Hz to MHz frequency range

Frequency Response Chart

The Impedance tab includes an interactive log-log chart showing capacitive reactance across the frequency spectrum, with a marker at your selected frequency.

Visual impedance analysis
Interactive frequency marker
Log-log scale display

Capacitor Combination

Add up to 10 capacitors with individual units and see the total equivalent capacitance for both series and parallel configurations, complete with the formula breakdown.

Up to 10 capacitors
Series and parallel modes
Formula breakdown display

Formula Display

Every result includes the formula used and step-by-step substitution, so you can verify the math and learn the relationships between capacitor parameters.

Complete formula breakdown
Step-by-step substitution
Educational transparency

Quick Examples

Pre-loaded examples for common circuits — power supply filters, audio crossovers, RF coupling, and more — help you get started quickly.

Power supply filters
Audio crossovers
RF coupling circuits

Privacy First

All calculations are performed in your browser. No data is sent to any server.

100% client-side processing
No data transmission
Complete privacy

Frequently Asked Questions

What is capacitance?

Capacitance (C) measures a capacitor's ability to store electrical charge. It is measured in farads (F). Common values range from picofarads (pF) in RF circuits to thousands of microfarads (µF) in power supplies.

Typical Ranges: RF circuits use pF to nF, audio circuits use nF to µF, and power supplies use hundreds to thousands of µF.

What is the relationship between Q, C, and V?

Charge (Q) equals capacitance (C) multiplied by voltage (V): Q = C × V. If you know any two of these three values, the calculator finds the third.

Fundamental Capacitor Equation

Q = C × V

Where:
Q = Charge (coulombs)
C = Capacitance (farads)
V = Voltage (volts)

What is capacitive reactance (Xc)?

Capacitive reactance is the opposition a capacitor presents to alternating current (AC). It depends on both the capacitance and the signal frequency: Xc = 1 / (2πfC). Higher frequency or larger capacitance means lower reactance.

Higher Reactance

Blocks AC

Low frequency
Small capacitance
High impedance

Lower Reactance

Passes AC

High frequency
Large capacitance
Low impedance

When should I use series vs. parallel capacitors?

Parallel capacitors add their values (C_total = C1 + C2 + ...), which is useful when you need a larger capacitance than any single component can provide. Series capacitors result in a smaller total value (1/C_total = 1/C1 + 1/C2 + ...), but can handle higher voltages since the voltage is shared across them.

Parallel Configuration

C_total = C1 + C2 + C3 + ...

Increases total capacitance
Same voltage across all
Used for larger capacitance

Series Configuration

1/C_total = 1/C1 + 1/C2 + ...

Decreases total capacitance
Voltage divides across all
Used for higher voltage rating

How is stored energy calculated?

The energy stored in a capacitor is E = ½ × C × V². This can also be expressed as E = ½QV or E = Q²/(2C). The calculator automatically shows the energy alongside any Basic mode result.

Energy Storage Formulas

E = ½ × C × V²
E = ½ × Q × V
E = Q² / (2C)

Where:
E = Energy (joules)
C = Capacitance (farads)
V = Voltage (volts)
Q = Charge (coulombs)

Safety Note: Large capacitors can store significant energy. Always discharge capacitors safely before handling, especially in high-voltage applications.

What units are supported?

The calculator supports a comprehensive range of SI units with automatic scaling to the most readable prefix:

Parameter	Supported Units	Typical Range
Capacitance	pF, nF, µF, mF, F	1 pF – 1 F
Voltage	mV, V, kV	1 mV – 100 kV
Charge	pC, nC, µC, mC, C	1 pC – 1 C
Frequency	Hz, kHz, MHz	1 Hz – 1 GHz

Auto-scaling: Results are automatically displayed in the most readable unit. For example, 0.001 µF becomes 1 nF, and 1000 pF becomes 1 nF.