Capacitor Code Calculator

Related tools: Resistor Color Code Calculator, Capacitor Bank Size Calculator, and Voltage Divider Calculator.

A capacitor code calculator converts a three-digit printed capacitor marking into its nominal capacitance value. For code 104, the calculated capacitance is 100,000 pF, which is also 100 nF or 0.1 µF.

That value is used when identifying replacement components, checking a bill of materials, troubleshooting control boards, verifying an RC timing network, matching capacitors in filters, and confirming whether a marked capacitor is suitable for the intended circuit position. Capacitance alone does not establish that a part is an acceptable replacement; voltage rating, dielectric type, polarity, tolerance, temperature behavior, and safety classification may also control the selection.

Three-Digit Capacitor Markings

The Capacitor code field decodes a common three-digit capacitor value marking. The first two digits are the significant value. The third digit is the multiplier, expressed as a power of ten in picofarads.

\(\displaystyle \text{Capacitance (pF)} = (\text{first two digits}) \times 10^{\text{third digit}}\)

For a capacitor code written as XYZ:

\(\displaystyle \text{Capacitance (pF)} = XY \times 10^Z\)

A marking of 104 therefore means:

\(\displaystyle 10 \times 10^4 = 100{,}000\ \text{pF}\)

The calculator reports the same physical capacitance in multiple units:

Result unit	Value for code 104
pF	100,000 pF
nF	100 nF
µF	0.1 µF

Unit conversion follows these relationships:

\(\displaystyle 1\ \text{nF} = 1{,}000\ \text{pF}\)

\(\displaystyle 1\ \text{µF} = 1{,}000\ \text{nF} = 1{,}000{,}000\ \text{pF}\)

Capacitor Code Input

Enter the three-digit marking in the Capacitor code field. For example, enter 104 when the component is marked 104.

The first two digits do not represent microfarads directly. Reading 104 as 10.4 µF would be incorrect. The final digit must be applied as a multiplier in picofarads.

Common examples include:

Capacitor code	Calculation	Capacitance
101	10 \times 10^1 pF	100 pF
102	10 \times 10^2 pF	1,000 pF / 1 nF
103	10 \times 10^3 pF	10,000 pF / 10 nF
104	10 \times 10^4 pF	100,000 pF / 100 nF / 0.1 µF
105	10 \times 10^5 pF	1,000,000 pF / 1 µF

A three-digit marking typically identifies a nominal capacitance value. It does not, by itself, establish the capacitor’s operating voltage, dielectric material, lead spacing, package type, polarity, frequency performance, surge capability, or safety approval.

Tolerance Code

Use the Tolerance code field to select the letter printed with the capacitor code. For example, select J = +/-5% when the component marking includes J.

The tolerance describes the permitted variation around the nominal value. A nominal 0.1 µF capacitor with a J tolerance has a permitted capacitance range of:

\(\displaystyle 0.1\ \text{µF} \times 5\% = 0.005\ \text{µF}\)

\(\displaystyle 0.1\ \text{µF} - 0.005\ \text{µF} = 0.095\ \text{µF}\)

\(\displaystyle 0.1\ \text{µF} + 0.005\ \text{µF} = 0.105\ \text{µF}\)

So the acceptable nominal tolerance range is:

\(\displaystyle 0.095\ \text{µF to } 0.105\ \text{µF}\)

Tolerance affects circuit behavior in applications such as timing circuits, oscillators, analog filtering, snubbers, motor controls, power supplies, and power-factor correction. A capacitor that has the correct nominal code but the wrong tolerance can shift timing, filtering, resonance, or control response.

Preferred Display Unit

The Preferred display unit field changes which result unit is emphasized. It does not change the capacitance calculation.

For code 104, selecting uF emphasizes the result as 0.1 µF. The calculator also reports 100 nF and 100,000 pF so that the component can be compared against schematic notes, manufacturer data sheets, parts lists, and replacement inventory expressed in different units.

In practical electrical and electronics work:

• pF is common for small-value capacitors used in RF, high-frequency, tuning, and signal applications.
• nF is common for ceramic bypassing, noise suppression, filtering, and control circuits.
• µF is common for larger filtering, coupling, timing, DC bus, motor, and power applications.

A 0.1 µF ceramic capacitor and a 100 nF capacitor have the same nominal capacitance. The different notation does not mean they are interchangeable without checking the rest of the component rating.

Calculation Example

Enter the following values:

Field	Value
Capacitor code	104
Tolerance code	J = +/-5%
Preferred display unit	uF

The calculator applies the three-digit marking formula:

\(\displaystyle 10 \times 10^4 = 100{,}000\ \text{pF}\)

The output is:

Result	Value
Capacitance	100,000 pF
Capacitance	100 nF
Capacitance	0.1 µF
Tolerance	5%
Preferred unit	uF

For a 5% tolerance, the nominal 0.1 µF value may range from 0.095 µF to 0.105 µF under the conditions used for the component’s rating and measurement specification.

Component Verification

The calculator performs code decoding only. Confirm the complete component marking and manufacturer data before installing a capacitor in a circuit.

Verify at least the following conditions:

• Voltage rating: The replacement must meet or exceed the required working-voltage rating, including expected transients where applicable.
• Dielectric and temperature behavior: Ceramic, film, electrolytic, mica, and other capacitor technologies can have very different stability, loss, frequency, DC-bias, and temperature characteristics.
• Polarity: Electrolytic and tantalum capacitors may be polarized. Reversing polarity can damage the component or create a safety hazard.
• Tolerance: Match the circuit requirement rather than assuming any tolerance is acceptable.
• Safety classification: Capacitors connected across or from line conductors in AC equipment may require a correctly rated safety capacitor for the intended location and duty.
• Physical construction: Confirm lead configuration, package dimensions, mounting arrangement, insulation, creepage and clearance requirements, and environmental suitability.
• Circuit duty: Check ripple current, inrush, pulse duty, frequency, dissipation, and ambient temperature where those conditions apply.

For building electrical work, capacitor selection in motor circuits, HVAC equipment, power-factor correction equipment, controls, and listed assemblies must be based on the equipment documentation, replacement specifications, applicable listing requirements, and the requirements enforced by the AHJ. The decoded capacitance value identifies one part of the component specification; it does not determine suitability for a branch circuit, feeder, motor circuit, or line-connected application.