Capacitor Calculator
Calculate capacitor stored charge Q=CV, energy E=½CV², and decode 3-digit capacitor codes with tolerance. Free online capacitor calculator for electronics and physics with interactive charts.
About This Calculator
The Capacitor Calculator is a comprehensive tool for electronics enthusiasts, students, and engineers who work with capacitors. It provides two essential modes: Capacitor Parameters to compute stored charge using Q = C × V and stored energy using E = ½ × C × V², and Capacitor Code Decoder to convert standard 3-digit EIA codes into actual capacitance values in pF, nF, or µF with tolerance interpretation.
The fundamental capacitor equation C = Q / V defines the relationship between capacitance, stored charge, and applied voltage. The calculator solves for charge and energy when you input any capacitance value and voltage. This is essential for designing power supply filter circuits, timing circuits, energy storage systems, and understanding how capacitors behave in DC and AC circuits. The code decoder follows the EIA-198 standard where the first two digits are significant figures and the third digit is a power-of-10 multiplier in picofarads.
Capacitors are passive electronic components that store electrical energy in an electric field. They are used in virtually every electronic device for filtering, coupling, decoupling, timing, and energy storage. Understanding the relationship between capacitance, voltage, charge, and energy is fundamental to circuit design and analysis.
Tolerance codes are critical when selecting capacitors for precision circuits such as oscillators, filter networks, and timing applications. The most common tolerance grades are J (±5%), K (±10%), and M (±20%). For ultra-precision applications, F (±1%) capacitors are available at higher cost.
Frequently Asked Questions
How do you calculate the charge stored in a capacitor?
The charge stored in a capacitor is calculated using the formula Q = C × V, where Q is the charge in coulombs, C is the capacitance in farads, and V is the voltage across the capacitor in volts. For example, a 100 µF capacitor charged to 12 V stores Q = 100 × 10⁻⁶ × 12 = 1.2 × 10⁻³ C of charge.
What does a 3-digit capacitor code like 104 mean?
A 3-digit capacitor code like 104 represents the capacitance in picofarads (pF). The first two digits are the significant figures (10), and the third digit is the multiplier (10⁴). So 104 means 10 × 10⁴ = 100,000 pF = 100 nF = 0.1 µF. Common codes include 104 (0.1 µF), 103 (10 nF), and 472 (4.7 nF).
How is energy stored in a capacitor calculated?
The energy stored in a capacitor is calculated using the formula E = ½ × C × V², where E is energy in joules, C is capacitance in farads, and V is voltage in volts. For a 100 µF capacitor at 12 V, E = 0.5 × 100 × 10⁻⁶ × 12² = 7.2 × 10⁻³ J.
What are the standard capacitor tolerance codes?
Standard capacitor tolerance codes include: F = ±1%, G = ±2%, J = ±5%, K = ±10%, M = ±20%, and Z = +80%/-20%. For smaller capacitors under 10 pF, letter codes represent absolute tolerances: B = ±0.1 pF, C = ±0.25 pF, and D = ±0.5 pF.
Can this calculator convert capacitor codes for any value?
Yes, the capacitor code decoder handles all standard 2-digit and 3-digit EIA capacitor codes. Enter a code like 104 or 472 and the calculator instantly converts it to µF, nF, and pF with tolerance. It also works in reverse to find the code from a known capacitance value.
What is the difference between capacitance and capacitive reactance?
Capacitance (C) is a capacitor's ability to store charge, measured in farads. Capacitive reactance (XC) is the opposition a capacitor offers to AC current, calculated as XC = 1/(2πfC) and measured in ohms. While capacitance is a fixed property of the component, reactance varies with frequency.
How do I identify a capacitor without labeled codes?
If a capacitor has no visible code, you can measure its capacitance using a multimeter with capacitance measurement mode. Alternatively, surface-mount capacitors often use a different coding system or no code at all. For electrolytic capacitors, the value and voltage rating are usually printed directly in µF and V.
What units does the capacitor calculator support?
The calculator accepts capacitance in microfarads (µF) for parameters mode and outputs results in farads (F), coulombs (C), and joules (J). The code decoder works with standard EIA codes and displays capacitance in pF, nF, and µF for convenience across all common unit systems.