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Capacitor Code Decoder

Decode a 3-digit ceramic capacitor code and tolerance letter to a value — or encode a capacitance back to its code.

Decoder Reference

Direction
Capacitance
100 nF
In picofarads
100000 pF
Tolerance
±10%
The 3-digit code gives capacitance in picofarads (first two digits × 10third). A trailing letter is the tolerance. Voltage codes vary by manufacturer — treat the rating as a guide.

How Capacitor Code Decoder works

Small ceramic and film capacitors are marked with a three-digit code because there is no room for a full value. The first two digits are significant figures and the third is the number of zeros to append, with the result always in picofarads. So 104 is 10 followed by four zeros — 100,000 pF, which is 100 nF, or 0.1 µF.

That picofarad base is the single most common source of confusion, because the values people actually talk about are in nanofarads and microfarads. Converting is a matter of moving the decimal point: 1 µF is 1,000 nF is 1,000,000 pF.

A letter after the digits gives tolerance, and the scheme is not the same as the resistor one. J is ±5%, K is ±10%, M is ±20%, and Z is the notably asymmetric −20%/+80% found on cheap high-capacitance ceramics. Values below 10 pF use letters for absolute tolerances instead: B is ±0.1 pF, C is ±0.25 pF, D is ±0.5 pF.

A third marking, the dielectric code, matters more than either. X7R, C0G/NP0, and Y5V describe temperature stability and are wildly different: C0G holds its value within ±30 ppm/°C, X7R varies ±15% across its range, and Y5V can lose 80% of its capacitance at temperature extremes. Class II dielectrics like X7R and Y5V also lose capacitance under applied DC voltage — often half or more at rated voltage.

Reference

  • Value in pF = (first two digits) × 10^(third digit)
  • 1 µF = 1,000 nF = 1,000,000 pF
  • Tolerance letters: J ±5%, K ±10%, M ±20%, Z −20%/+80%
  • Small-value letters: B ±0.1 pF, C ±0.25 pF, D ±0.5 pF
  • Common codes: 104 = 100 nF, 103 = 10 nF, 102 = 1 nF, 221 = 220 pF

How to use this decoder

  1. Read the printed code

    Enter the three digits and any tolerance letter exactly as marked on the capacitor body.

  2. Read the decoded value

    The result is shown in pF, nF, and µF at once, so it matches whichever unit your schematic uses.

  3. Or encode a value

    Enter a capacitance to get the code that would be printed on the corresponding part.

  4. Check the dielectric

    Note the dielectric code separately — it determines whether the marked value survives real operating conditions.

Worked examples

The ubiquitous decoupling capacitor

Given
Code 104
Result
100,000 pF = 100 nF = 0.1 µF

The most common capacitor in digital electronics, sitting beside almost every IC supply pin.

A small timing capacitor

Given
Code 221J
Result
220 pF ±5%

Two digits and one zero. The J tolerance suits filter and timing work where the value must be predictable.

DC bias loss

Given
A 10 µF X5R 0805 rated 6.3 V, operated at 5 V
Result
Effective capacitance may be under 3 µF

Not a fault — it is inherent to Class II ceramics. Choose a higher voltage rating or a larger package to keep the capacitance you designed for.

When to use it

  • Identifying an unmarked capacitor from a parts bin before fitting it.
  • Confirming that the part on a board matches the value in the schematic.
  • Converting between pF, nF, and µF when a datasheet and a schematic disagree on units.
  • Finding the printed code for a value you need to search for in stock.
  • Understanding tolerance and dielectric markings when selecting a replacement.

Things to watch out for

  • Codes are always in picofarads. Reading 104 as 104 µF instead of 100 nF is off by six orders of magnitude.
  • A two-digit marking is the value in picofarads directly: 47 means 47 pF, not 47 × 10^0 by the three-digit rule.
  • The dielectric code matters as much as the value. Y5V parts can lose most of their capacitance across temperature and applied voltage; C0G/NP0 barely changes.
  • Electrolytic and tantalum capacitors are marked with their value printed plainly, plus a voltage rating and a polarity stripe. Fitting a polarised part backwards is a failure and often a violent one.

Frequently asked questions

What does 104 mean on a capacitor?

100 nF, equivalently 0.1 µF or 100,000 pF. The first two digits are significant figures and the third is the number of zeros to append, with the total always expressed in picofarads.

What does the letter after the code mean?

Tolerance. J is ±5%, K is ±10%, M is ±20%, and Z is −20%/+80%. Below 10 pF the letters mean absolute tolerances instead: B is ±0.1 pF, C is ±0.25 pF, D is ±0.5 pF.

How do I convert pF to nF and µF?

Divide by 1,000 to go from pF to nF, and by 1,000 again for µF. So 100,000 pF is 100 nF is 0.1 µF. All three describe the same part; which one appears depends on regional and industry convention.

What is the difference between X7R and C0G?

C0G (also called NP0) is a Class I dielectric: extremely stable, within about ±30 ppm/°C, with negligible voltage and ageing effects, but only available at small values. X7R is Class II: much higher capacitance in the same package, at the cost of ±15% over temperature and significant loss under DC bias.

Why is my measured capacitance lower than marked?

Most likely DC bias loss, if it is a Class II ceramic. Applying voltage to X5R, X7R, or Y5V dielectric reduces its capacitance, sometimes by more than half at the rated voltage. Ageing and temperature contribute as well.

Do electrolytic capacitors use this code?

No. They are large enough to print the value, voltage rating, and temperature grade directly, along with a stripe marking the negative terminal. The three-digit code is for small ceramic and film parts only.

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