Ceramic Capacitor Code Converter (Code to Capacitance & Capacitance to Code)
Decode a 3-digit ceramic capacitor code like "104" into pF, nF, and µF instantly, or convert a capacitance back into the standard code. Includes a tolerance letter table.
Tolerance letter reference (EIA standard)
| Letter | Tolerance |
|---|---|
| B | ±0.1pF |
| C | ±0.25pF |
| D | ±0.5pF |
| F | ±1% |
| G | ±2% |
| J | ±5% |
| K | ±10% |
| M | ±20% |
| Z | +80% / -20% |
What Is a Ceramic Capacitor Code? Reading Capacitance from a 3-Digit Number
A ceramic capacitor's body is stamped with a compact 2- or 3-digit number — a marking that plays the same role as the color bands on a resistor, just written in digits instead of colors. The first two digits are the significant figures, and the last digit is a power-of-ten multiplier expressed in picofarads (pF). Multiply the two together and you get the capacitance: "104", for instance, works out to 10 × 10^4 = 100,000pF = 100nF = 0.1µF. This scheme lets anyone read a part's value straight off the case without ever having to desolder it from the board.
This tool covers both directions of that conversion. The "Code → Capacitance" mode takes the digits printed on a part and instantly returns the capacitance in pF, nF, and µF together, while "Capacitance → Code" runs the process in reverse, working out the standard code for a target value you specify. Along the way it also handles the well-known exception where the final digit is "9", and decodes the trailing tolerance letter (J, K, M, and others) so you can read a capacitor's marking with confidence rather than guesswork.
How to Read and Look Up a Capacitor Code
- Pick a calculation mode Choose "Code → Capacitance" if you have a part in hand and want to know its value, or "Capacitance → Code" if you already know the capacitance you need and want the matching standard code.
- Enter the code or the capacitance For "Code → Capacitance", type the 2- or 3-digit number stamped on the part (e.g. 104), plus the trailing tolerance letter if there is one. For "Capacitance → Code", enter a numeric value and pick its unit.
- Watch for the "9" multiplier exception When the third digit is a "9", it means ×10^-1 (multiply by 0.1) rather than ×10^9 — a special case worth checking for before you read the result, since it's easy to misinterpret.
- Check the calculated result The tool displays the capacitance in pF, nF, and µF together, or the matching standard code, depending on which mode you chose. If you supplied a tolerance letter, its meaning is shown alongside the result.
- Cross-check against the tolerance letter table Use the on-page tolerance letter reference (EIA standard) to look up exactly what margin of error the single trailing letter represents.
Tips for getting more out of it
- The only exception is a third digit of "9", which means ×10^-1 (multiply by 0.1), not ×10^9. So "339" is 33 × 0.1 = 3.3pF.
- A 2-digit code like "47" has no multiplier at all — it's simply the pF value directly. This is common on very small ceramic capacitors under 10pF.
- The trailing letter is a tolerance code. General-purpose parts commonly use K (±10%) or M (±20%), while precision parts use J (±5%) or F (±1%).
- The "Capacitance to Code" mode always produces a standard 3-digit code. If your input doesn't fit cleanly into 2 significant figures, it gets rounded to the nearest representable value.
- If a marking like "104" is too worn or small to read clearly, measure the capacitance with a multimeter and cross-check it using the "Capacitance to Code" mode.
When This Tool Comes in Handy
Picking parts for an electronics project
Read the capacitance off a capacitor you have on hand and confirm it matches the value called for in your schematic before you solder it in.
Identifying parts during board repair
If you can make out the marking on a ceramic capacitor on a failed board, you can immediately work out the capacitance you need in order to source a replacement.
Working out values at the design stage
When a decoupling capacitor or filter circuit calls for a specific capacitance, use the "Capacitance → Code" mode ahead of time to find the standard code to specify when ordering or sourcing parts.
Inspecting incoming stock
When you receive a batch of ceramic capacitors from a supplier, read the codes stamped on them to verify the capacitance matches what you actually ordered.
Teaching or learning the code in a lab setting
Electronics students can use real examples to learn the "9" multiplier exception and what the tolerance letters mean, rather than just memorizing the rules abstractly.
Glossary
- EIA code
- A 3-digit numeric code, standardized by the Electronic Industries Alliance (EIA), that expresses a ceramic capacitor's capacitance as two significant digits followed by a single multiplier digit. JIS (Japan's industrial standard) uses essentially the same scheme.
- Tolerance letter
- A single letter printed after the numeric code that shows how far the actual capacitance may deviate from the labeled value. J (±5%), K (±10%), and M (±20%) are the most common; very small parts sometimes use an absolute value in pF instead.
- pF (picofarad)
- The base unit of capacitance used in these codes — one trillionth of a farad (F). The entire capacitor code system is built around pF as its reference unit.
- nF (nanofarad)
- A unit equal to 1,000pF, or one-thousandth of a µF. It is commonly used for values that fall between the pF and µF ranges.
- µF (microfarad)
- A unit equal to 1,000,000pF. It is the unit most often used for larger-value parts such as electrolytic capacitors.
- Ceramic capacitor
- A small capacitor that uses a ceramic material as its dielectric. Because it is inexpensive and compact, it is used extensively in electronic circuits, especially for decoupling and noise suppression.
- Multiplier digit
- The third digit of the code, representing a power of ten. Digits 0 through 8 are used directly as the exponent, but 9 is a special exception meaning ×10^-1 (multiply by 0.1).
- Decoupling capacitor (bypass capacitor)
- A capacitor placed close to an IC to filter noise on the power supply line and absorb momentary voltage fluctuations. 104 (0.1µF) is one of the most commonly used values for this purpose.
Frequently Asked Questions
Side Note — A Capacitor Code Is the Numeric Cousin of the Resistor Color Code
Most ceramic capacitors are tiny, and like resistors, there simply isn't room to print the full capacitance value in text. So the EIA (Electronic Industries Alliance) and JIS (Japanese Industrial Standards) standardized a compact 3-digit numeric code combining two significant digits with a single multiplier digit — a similar idea to the resistor color code, just expressed with numbers and a letter instead of colored bands. Both systems solve the same underlying problem: packing a lot of information onto a very small part.
The trickiest part of this 3-digit system is what happens when the multiplier digit is "9". Digits 0 through 8 are used directly as a power of ten, but 9 is a special case meaning ×10^-1 (0.1×) rather than ×10^9. Misreading "339" as 33 × 10^9 pF instead of the correct 3.3pF would be off by many orders of magnitude — a mistake that's common enough to be called out explicitly in many textbooks and datasheets as a classic beginner pitfall.
Capacitor code tables are a standard fixture in electronics hobbyist sites and datasheet appendices, often presented right alongside resistor color code charts. But actually keying in the code printed on a real part to check its value — or working the other direction from a desired capacitance to a standard code — is something a static reference table alone can't do. Paired with the resistor color code calculator in the same physics category, this tool rounds out the basic lookup work involved in reading passive components.