Capacitor Calculator

MiniWebtool’s Capacitor Calculator brings common capacitor calculations and code reading into one tool. Select a mode for the available capacitance, voltage, frequency, or resistance values, or decode a printed capacitor marking.

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Help me understand MiniWebtool's Capacitor Calculator: https://miniwebtool.com/capacitor-calculator/. What can I use it for, what inputs or settings do I need, and how do I use it and understand the output? Walk me through one simple example. Use this page as your source and answer in English.

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100 µF at 12 V: charge 1.2 mC, stored energy 7.2 mJ

Choose what to calculate, then enter capacitance and voltage with their units.

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About Capacitor Calculator

The Capacitor Calculator is a comprehensive tool designed for electrical engineers, electronics hobbyists, and students who need to quickly determine the electrical properties of capacitors. Whether you're designing a power supply filter, selecting a coupling capacitor for an audio circuit, or decoding the markings on a ceramic disc capacitor, this calculator provides instant, accurate results with step-by-step explanations.

At a Glance

Capacitor Calculator computes the stored charge, stored energy, capacitive reactance and RC time constant of a capacitor. A second mode decodes 3-digit ceramic capacitor codes such as 104 and 473.

Capacitor Calculator: features at a glance
Feature	What you get	Good for
Capacitance units	Enter capacitance in pF, nF, µF, mF or F, and the applied voltage in volts.	Working with values from small ceramics to large electrolytics
Charge and energy	Stored charge uses Q = C × V in coulombs. Stored energy uses E = ½CV² in joules.	Sizing energy storage or backup capacitors
Capacitive reactance	Enter a frequency to get Xc = 1/(2πfC), the capacitor's AC opposition in ohms.	Designing filters and coupling stages
RC time constant	Enter a resistance to get τ = R × C, with charging milestones. One time constant reaches about 63.2% of the final voltage.	Timing circuits and debouncing
Code decoder	Reads 3-digit codes: two significant digits and a multiplier in pF, so 104 is 100 nF. A letter suffix gives tolerance: J ±5%, K ±10%, M ±20%.	Identifying unmarked ceramic capacitors in a parts bin
Steps and diagram	An animated capacitor diagram and a step-by-step breakdown show how each value was derived.	Students checking their working

What is a Capacitor?

A capacitor is a passive electronic component that stores electrical energy in an electric field between two conductive plates separated by an insulating material called a dielectric. When voltage is applied across the plates, positive charges accumulate on one plate and negative charges on the other, creating an electric field that stores energy. Capacitance, measured in farads (F), represents a capacitor's ability to store charge per unit voltage.

Key Capacitor Formulas

Capacitor Calculator: Key Capacitor Formulas
Property	Formula	Description
Stored Charge	\( Q = C \times V \)	Charge in coulombs
Stored Energy	\( E = \frac{1}{2}CV^2 \)	Energy in joules
Capacitive Reactance	\( X_C = \frac{1}{2\pi fC} \)	AC impedance in ohms
RC Time Constant	\( \tau = R \times C \)	Time to reach 63.2% charge

Types of Capacitors

Capacitors come in many forms, each optimized for specific applications:

Ceramic Capacitors — Small, inexpensive, and ideal for high-frequency decoupling. Common values range from 1 pF to 100 µF. Often marked with 3-digit codes (e.g., 104 = 100 nF).
Electrolytic Capacitors — Polarized capacitors offering high capacitance (1 µF to 10,000 µF) for power supply filtering and energy storage. Available in aluminum and tantalum varieties.
Film Capacitors — Known for stability and low losses, used in audio circuits, motor run applications, and power electronics. Values typically range from 1 nF to 100 µF.
Tantalum Capacitors — Compact, high-capacitance components used in portable electronics. Offer excellent stability but require careful voltage derating.
Supercapacitors — Ultra-high capacitance (0.1 F to 3000 F) devices bridging the gap between capacitors and batteries, used for energy harvesting and backup power.

How to Read Capacitor Codes

Ceramic capacitors often use a 3-digit code system where the first two digits represent the significant figures and the third digit is the multiplier (number of zeros to add), giving the value in picofarads (pF):

Capacitor Calculator: How to Read Capacitor Codes
Code	Calculation	Value
104	10 × 10⁴ pF	100,000 pF = 100 nF = 0.1 µF
473	47 × 10³ pF	47,000 pF = 47 nF = 0.047 µF
222	22 × 10² pF	2,200 pF = 2.2 nF
101	10 × 10¹ pF	100 pF = 0.1 nF

A letter suffix may indicate tolerance: J (±5%), K (±10%), M (±20%). For example, "104K" means 100 nF with ±10% tolerance.

How to Use This Calculator

Select a mode — Choose "Calculator" for property calculations or "Code Decoder" to decode ceramic capacitor markings.
Enter capacitance and voltage — In Calculator mode, input your capacitance value with the appropriate unit (pF, nF, µF, mF, or F) and the applied voltage in volts.
Add optional parameters — Enter a frequency to calculate capacitive reactance, or a resistance value to calculate the RC time constant.
Click Calculate — Press the Calculate button to see detailed results including stored charge, energy, reactance, and time constant.
Review step-by-step results — Examine the detailed calculation breakdown to understand how each value was derived.

Understanding Capacitive Reactance

Capacitive reactance (\(X_C\)) is the opposition a capacitor presents to alternating current (AC). Unlike resistance, reactance varies with frequency — at higher frequencies, a capacitor presents less opposition to current flow. This property makes capacitors essential for frequency-dependent circuits like filters, coupling stages, and tuning circuits. At DC (0 Hz), a capacitor has infinite reactance, effectively blocking direct current while passing AC signals.

RC Time Constant

When a capacitor charges or discharges through a resistor, the rate of voltage change follows an exponential curve defined by the time constant \(\tau = RC\). After one time constant, the capacitor reaches approximately 63.2% of its final voltage. Practical rule of thumb: a capacitor is considered fully charged after \(5\tau\) (99.3%). This principle is fundamental in timing circuits, filters, debouncing, and power supply design.

Common Capacitor Values and Applications

Capacitor Calculator: Common Capacitor Values and Applications
Value	Code	Typical Application
22 pF	220	Crystal oscillator load capacitor
100 nF (0.1 µF)	104	IC decoupling / bypass capacitor
1 µF	105	Audio coupling, small filtering
10 µF	—	Voltage regulator output filtering
100 µF	—	Power supply bulk filtering
470 µF	—	Motor start, heavy filtering

Frequently Asked Questions

What is capacitance and how is it measured?

Capacitance is the ability of a component to store electrical charge. It is measured in farads (F), where one farad equals one coulomb of charge stored per volt applied. In practice, most capacitors have values in picofarads (pF), nanofarads (nF), or microfarads (µF), as one farad is an extremely large capacitance.

How do I read a 3-digit capacitor code?

The first two digits are the significant figures and the third digit is the multiplier (the power of 10 to multiply by), giving the capacitance in picofarads. For example, code 104 means 10 × 10⁴ = 100,000 pF = 100 nF = 0.1 µF.

What is capacitive reactance and why does it matter?

Capacitive reactance is the frequency-dependent opposition a capacitor presents to AC current, calculated as Xc = 1/(2πfC). It matters because it determines how a capacitor behaves in AC circuits — lower reactance at higher frequencies means the capacitor passes high-frequency signals more easily, which is the basis for filter design.

What is the RC time constant?

The RC time constant (τ = R × C) is the time it takes for a capacitor to charge to approximately 63.2% of the applied voltage through a resistor, or to discharge to 36.8% of its initial voltage. After five time constants (5τ), the capacitor is considered fully charged or discharged at 99.3%.

What are typical capacitor values for common applications?

Common values include 100 nF (0.1 µF) for digital IC decoupling, 10–22 µF for voltage regulator input/output filtering, 100–1000 µF for power supply bulk filtering, 22–33 pF for crystal oscillator load capacitors, and 1–10 µF for audio coupling between amplifier stages.

How much energy can a capacitor store?

The energy stored in a capacitor is calculated using E = ½CV². A typical 100 µF capacitor charged to 12V stores 7.2 millijoules. While this seems small, supercapacitors rated at thousands of farads can store significant energy — a 3000F supercapacitor at 2.7V stores over 10 kilojoules, enough to power small devices for minutes.

Reference this content, page, or tool as:

"Capacitor Calculator" at https://MiniWebtool.com/capacitor-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: Mar 17, 2026

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