Free Capacitor Calculator

The capacitor calculator is a unified online tool designed to address three common capacitor‑related needs: interpreting the three‑digit markings found on many capacitors, converting between a capacitance value and its corresponding code in either direction, and calculating the amount of stored electric charge when both capacitance and voltage are provided. It effectively serves as a capacitor code calculator, a capacitance calculator, a capacitor code converter, and a capacitor charge calculator all within a single interface.

Basic Capacitance Formula

All capacitors operate according to the fundamental relationship

$$C = \frac{Q}{V}$$

where $C$ is the capacitance (measured in farads), $Q$ is the electric charge stored in the element (coulombs), and $V$ is the voltage applied across its terminals. The equation illustrates that a capacitor is a passive component that stores charge whenever a voltage is impressed upon it. This principle holds true regardless of the physical construction—parallel‑plate, cylindrical, or spherical—and also applies when capacitors are combined in series or parallel (in which case the combination behaves as a single equivalent capacitor with a total capacitance that can be found using standard series/parallel formulas).

Decoding the Three‑Digit Capacitor Code

For capacitors rated below 100 µF, the capacitance is often indicated by a compact three‑digit code. The decoding rule is straightforward:

• The first two digits form the significant figure of the capacitance in picofarads (pF).
• The third digit $n$ acts as the multiplier (power of ten), i.e., multiply the significant figure by $10^{n}$.

Example: Code 104
Digits: “10” → base value 10 pF; third digit “4” → multiplier $10^{4}$.
Result: $10 \times 10^{4}\ \text{pF} = 10^{5}\ \text{pF} = 100\ \text{nF} = 0.1\ \mu\text{F}$.

If the marking contains only one or two digits, those digits directly give the value in pF.

Converting a Capacitance Value to Its Code (Reverse Conversion)

The same calculator works in the opposite direction. To obtain the three‑digit code for a known capacitance:

1. Round the capacitance to two significant digits (if necessary).
2. Express the value in pF and write it in the form $m \times 10^{e}$, where $m$ is a number between 10 and 99 (the two‑digit base) and $e$ is the exponent (the third digit).

Example: 1.2 µF (rounded from 1.24 µF)
$1.2\ \mu\text{F} = 1,\!200,\!000\ \text{pF} = 12 \times 10^{5}\ \text{pF}$ → code 125.

Tolerance Letter Codes

Immediately following the three‑digit numeric code, a letter often specifies the allowed tolerance (the range within which the actual capacitance is guaranteed to lie). The following table summarizes the most common tolerance codes:

Letter	Tolerance
B	±0.1 pF
C	±0.25 pF
D	±0.5 pF
F	±1%
G	±2%
J	±5%
K	±10%
M	±20%
Z	+80%/−20%

Example: 104K
Nominal capacitance: 100 nF (from code 104). Tolerance: ±10% → lower limit 90 nF, upper limit 110 nF.

When you enter a code that includes the tolerance letter, the tool automatically displays both the nominal value and the acceptable range.

Stored Charge Calculation

The calculator also fulfills the need of a capacitor charge calculator. Using the relation

$$Q = C \times V,$$

it computes the electric charge $Q$ (in coulombs) stored in a capacitor when you supply the capacitance $C$ and the voltage $V$. This feature is valuable for estimating energy storage and for circuit‑analysis tasks.

Summary

By integrating code interpretation, bidirectional code–capacitance conversion, and charge computation, this capacitor calculator offers a convenient, all‑in‑one solution for students, hobbyists, and professionals. Whether you need to quickly decipher a component marking, double‑check a replacement part’s value, or estimate stored charge, the tool delivers fast and accurate results.