ElectroHub

Capacitor Code Calculator

Small ceramic capacitors carry a three-digit code rather than a printed value. The first two digits are significant, the third is a power-of-ten multiplier, and the result is in picofarads — which is where most of the confusion starts.

Capacitor Code

Type the marking printed on the capacitor — e.g. 104 (100 nF), 472K (4.7 nF ±10%), 4R7 (4.7 pF).

Capacitance
In picofarads
  1. 1.FormulaC = first two digits × multiplier digit (in pF)SubstituteC = 10 ×10^4 (third digit 4 → ×10^4)ResultC = 100000 pF
  2. 2.Convert: 100000 pF = 100 nF

The formula

Value in pF = (first two digits) × 10^(third digit)

Digits 1–2
significant figures
Digit 3
number of zeros to append (multiplier)
Letter
tolerance code, e.g. J = ±5 %, K = ±10 %, M = ±20 %

Worked example

A capacitor marked 104.

  1. Significant digits: 10
  2. Multiplier: ×10⁴
  3. 10 × 10000 = 100000 pF
  4. Convert: 100000 pF = 100 nF = 0.1 µF

100 nF — the ubiquitous decoupling capacitor.

Where you'll use it

Identifying parts from a mixed bag and reading schematics that mix pF, nF and µF conventions. Codes below 100 are usually the value in pF directly: a part marked 47 is 47 pF, not 47 × 10⁷.

The laws behind it

Parts this applies to

Capacitor (ceramic / MLCC)Capacitor (aluminium electrolytic)Capacitor (tantalum)Capacitor (film)SupercapacitorQuartz Crystal / ResonatorMOSFET555 Timer IC

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