The direct answer to reading a standard 3-digit capacitance code is this: take the first two digits as your base significant figures, add the third digit as the number of trailing zeros, and the result is your capacitance in picofarads (pF). For example, a capacitor marked 104 means 10 followed by four zeros (100,000 pF), which converts to 100 nF or 0.1 µF. If a letter follows the numbers, it denotes the tolerance (e.g., 'K' means ±10%).
How to Read the EIA Capacitance Code Chart
Because ceramic and film capacitors are often too small to print full alphanumeric values like '0.1µF 50V', the industry relies on the EIA RS-198 standard (harmonized with IEC 60062) to compress this data into a 2- or 3-digit code. When looking at the master chart below, the Code column is what you see printed on the component. The Multiplier column tells you how many zeros to append to the first two digits. The final columns provide the converted values in nanofarads (nF) and microfarads (µF), which are the units you will actually use when calculating RC time constants or filter cutoff frequencies.
Capacitor math trips up many hobbyists because of the unit jumps. Remember: 1,000 pF = 1 nF. And 1,000 nF = 1 µF. If your multimeter reads in nF and your schematic calls for 0.1 µF, you are looking for 100 nF, which is coded as 104.
The Master Capacitance Code Chart (EIA RS-198)
Below is the complete reference table for the most common EIA capacitance codes found on ceramic disc, multilayer ceramic (MLCC), and tantalum capacitors. I have embedded bookmark-friendly anchor IDs on the most frequently queried values so you can jump straight to them.
| Printed Code | Significant Figures | Multiplier (Zeros) | Total Capacitance (pF) | Equivalent (nF) | Equivalent (µF) |
|---|---|---|---|---|---|
| 101 | 10 | 0 | 100 pF | 0.1 nF | 0.0001 µF |
| 102 | 10 | 00 | 1,000 pF | 1 nF | 0.001 µF |
| 103 | 10 | 000 | 10,000 pF | 10 nF | 0.01 µF |
| 104 | 10 | 0000 | 100,000 pF | 100 nF | 0.1 µF |
| 105 | 10 | 00000 | 1,000,000 pF | 1,000 nF | 1.0 µF |
| 221 | 22 | 0 | 220 pF | 0.22 nF | 0.00022 µF |
| 222 | 22 | 00 | 2,200 pF | 2.2 nF | 0.0022 µF |
| 223 | 22 | 000 | 22,000 pF | 22 nF | 0.022 µF |
| 224 | 22 | 0000 | 220,000 pF | 220 nF | 0.22 µF |
| 331 | 33 | 0 | 330 pF | 0.33 nF | 0.00033 µF |
| 332 | 33 | 00 | 3,300 pF | 3.3 nF | 0.0033 µF |
| 333 | 33 | 000 | 33,000 pF | 33 nF | 0.033 µF |
| 471 | 47 | 0 | 470 pF | 0.47 nF | 0.00047 µF |
| 472 | 47 | 00 | 4,700 pF | 4.7 nF | 0.0047 µF |
| 473 | 47 | 000 | 47,000 pF | 47 nF | 0.047 µF |
| 474 | 47 | 0000 | 470,000 pF | 470 nF | 0.47 µF |
| 561 | 56 | 0 | 560 pF | 0.56 nF | 0.00056 µF |
| 681 | 68 | 0 | 680 pF | 0.68 nF | 0.00068 µF |
| 682 | 68 | 00 | 6,800 pF | 6.8 nF | 0.0068 µF |
| 822 | 82 | 00 | 8,200 pF | 8.2 nF | 0.0082 µF |
Tolerance, Voltage, and Dielectric Modifiers
A common misconception is that the letters following the 3-digit code act as 'derating rows' that modify the base capacitance value. They do not. Instead, these modifiers define the tolerance (how much the actual value can deviate from the printed code) and the dielectric class (which dictates how the capacitor behaves under temperature and voltage stress).
Tolerance Letters
If you see a 104K, the 'K' means the actual capacitance is guaranteed to be within ±10% of 100 nF (meaning it could measure anywhere from 90 nF to 110 nF on your LCR meter). Here are the standard EIA tolerance codes:
- J = ±5% (Common on C0G/NP0 precision caps)
- K = ±10% (The most common tolerance for general-purpose X7R caps)
- M = ±20% (Standard for high-value electrolytics and some MLCCs)
- Z = +80% / -20% (Often found on cheap Y5V decoupling caps; avoid for timing circuits)
Dielectric Codes and Voltage Derating
While the 3-digit code gives you the nominal value at 0V DC bias and 25°C, the dielectric material determines how much capacitance you actually lose when you apply voltage. According to Murata's technical guidelines on ceramic capacitors, high-capacitance Class II dielectrics suffer from severe DC bias derating.
- C0G / NP0 (Class I): Extremely stable. A 100 pF C0G cap will remain 100 pF regardless of applied voltage or temperature swings. Use these for RF filters and 555 timer oscillators.
- X7R / X5R (Class II): The workhorses of PCB decoupling. However, a 10 µF X5R capacitor in a 0805 package might lose up to 50% of its capacitance when operated near its rated voltage.
- Y5V (Class III): High nominal capacitance but terrible stability. A Y5V cap can lose 80% of its value just by heating up to 50°C. Never use these in critical analog paths.
What the Capacitance Code Cannot Tell You
Relying solely on the printed capacitance code is a fast way to debug a digital logic circuit, but it is entirely insufficient for power supply design or precision analog work. Here is what the EIA code leaves out, forcing you to consult the manufacturer datasheet:
- DC Bias Derating Curves: As mentioned, the code assumes 0V bias. If you are designing a 12V buck converter and need 10 µF of output capacitance, putting in a '106' (10 µF) X5R MLCC rated for 16V will likely yield only 3 µF in practice. You must check the DC bias graph in the datasheet.
- Equivalent Series Resistance (ESR): Two capacitors marked '104K' from different manufacturers (or even different package sizes from the same manufacturer) will have vastly different ESR. Low ESR is critical for switching power supply ripple filtering.
- Microphonic Effects: Class II ceramic capacitors (like X7R) exhibit piezoelectric properties. They can act as microphones, picking up mechanical vibration and injecting it into your circuit as electrical noise, or conversely, they can 'sing' audibly when subjected to PWM frequencies.
- AC vs. DC Voltage Ratings: A capacitor marked with a 50V DC rating may suffer dielectric breakdown at much lower AC RMS voltages due to the continuous polarity reversal stressing the dielectric layer.
Frequently Asked Questions
How do I read a 4-digit capacitance code on a surface mount capacitor?
Some high-precision or specialized MLCCs use a 4-digit code. The rule remains the same, but the first three digits are significant figures, and the fourth digit is the multiplier. For example, a code of 1001 means 100 followed by one zero, equaling 1,000 pF (1 nF). A code of 4702 means 470 followed by two zeros, equaling 47,000 pF (47 nF). This system is mostly used when tighter E12/E24 series values are required that don't fit the standard 2-significant-digit format.
What does the letter 'J' or 'K' mean on a ceramic capacitor?
These letters indicate the manufacturing tolerance of the capacitor. 'J' means the actual measured capacitance will be within ±5% of the nominal value printed on the part. 'K' means ±10%. If you are building an active audio filter where the cutoff frequency depends on exact RC values, you should hunt down 'J' tolerance parts (usually C0G/NP0 dielectric). If you are just bulk-decoupling a microcontroller's VCC pin, 'K' or even 'M' (±20%) is perfectly acceptable and much cheaper.
Why does my 104 capacitor measure lower than 100nF on my multimeter?
If your 104 (100 nF) capacitor measures at 85 nF on your bench multimeter, there are three likely culprits. First, check the tolerance; if it is marked 104M, a 15% deviation is within spec. Second, cheap multimeters measure capacitance using a low-frequency charge/discharge cycle that can be skewed by parallel leakage resistance or high ESR. Third, if the capacitor is still soldered into the circuit, parallel PCB traces and other components are skewing the reading. Always measure capacitance with the component completely isolated from the circuit, and ideally use a dedicated LCR meter at 1 kHz or 100 kHz.
Is there a difference between a 104K and 104M capacitor?
Yes, the difference is strictly in the guaranteed tolerance band. Both have a nominal capacitance of 100,000 pF (100 nF). The 104K guarantees the value is between 90 nF and 110 nF. The 104M guarantees the value is between 80 nF and 120 nF. In automated PCB assembly, 104K is the standard for general decoupling, while 104M is often used in non-critical applications where the manufacturer wants to save a fraction of a cent per component by accepting a wider factory sorting bin.
