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Components / Capacitors

Capacitor Marking Code

Decode capacitor markings, including their genuinely ambiguous readings, with 3-digit pF, RKM and EIA-198 support.

Marking on the component

Case matters for EIA-198 codes. Add any printed tolerance, voltage and dielectric, for example 104K 50V X7R.

Accepted formats
104K 50V X7R4n7L4KA3
104K50VX7R

Decoded nominal value

100 nF

3-digit pF code

Decoded nominal value

100 nF

Decoded nominal value100 nF
Detected format3-digit pF code
Tolerance±10%
Marked voltage rating50 V
DielectricX7R
Rule applied10 × 10⁴ pF

Component guide

Read a capacitor marking without over-interpreting it

A capacitor marking may identify capacitance and sometimes tolerance, rated voltage, or dielectric. It almost never identifies the exact part: technology, polarity, ESR, package, and approvals must be checked separately.

Method and assumptions

Three-digit codes use two significant figures and the number of zeros in pF: 104 is 10 × 10⁴ pF, or 100 nF. RKM notation uses p, n, or µ as the decimal separator and unit, for example 4n7. Two-character EIA-198 codes combine an alphabetic mantissa with a multiplier; case matters for some legacy mantissas.

Inputs to verify

Complete, faithful marking

Transcribe letters, digits, and units exactly, including lower-case letters, then include printed voltage or dielectric codes. Never turn a manufacturer mark, lot code, or date code into a value without the datasheet.

Mechanical and electrical context

Record technology, polarity, footprint, and the relevant rail. The same text can be ambiguous: 104 can also be an SMD-resistor code, and X2 can designate a mains safety class.

Recommended workflow

  1. 1Enter the marking: the decoder shows every plausible standard interpretation instead of hiding an ambiguity.
  2. 2Check tolerance, voltage, and dielectric only when they are actually printed; never assume a blank field.
  3. 3Then confirm the package, technology, polarity, and datasheet before working on the component.

Checkable example

104K 50V X7R reads as 100 nF, ±10%, 50 V, X7R dielectric. Effective X7R capacitance still depends on DC bias, temperature, and manufacturer: nominal capacitance does not guarantee in-circuit capacitance.

Limits to keep in mind

This decoder covers common conventions, not every proprietary code. It does not measure ESR, leakage, ripple-current capability, or pulse rating. Safety, electrolytic, and tantalum capacitors need particular attention to polarity, approvals, and surge conditions.

Frequently asked questions

What does 104 mean?

In the standard three-digit format, 104 is 100,000 pF, or 100 nF / 0.1 µF. A bare three-digit print can still be ambiguous on some parts; verify the context and part number.

Can I replace an X7R with the same marked capacitance?

Not automatically. At minimum compare voltage, effective capacitance under DC bias, temperature, package, tolerance, and impedance/ESR at the relevant frequency. A C0G, X7R, and electrolytic with the same nominal value do not behave alike.

References to consult

  • Method references: EIA-198 / IEC 60062 for marking, plus the manufacturer datasheet for voltage, dielectric, ESR, DC-bias limits, and approvals.
  • For a critical replacement, also compare the schematic, BOM, actual package, and temperature, ripple, and surge requirements.

Original educational content, reviewed for technical clarity on 20 August 2026. Always verify datasheets, applicable standards, and your design before power-up or manufacture.