Capacitor Guide
How to Read Capacitor Codes
Learn how to decode common capacitor markings, convert capacitance units, identify tolerance codes, and verify capacitor values.
- Reading Time
- 12 min
- Difficulty
- Beginner
- Last Updated
- July 15, 2026
Introduction
Capacitors are often too small to print a full value, voltage rating, tolerance, dielectric type, and manufacturer information on the body. Instead, many ceramic and film capacitors use compact numeric markings. The marking is useful, but it is only the first step in identifying the part.
Engineers should decode the capacitance, then verify tolerance, voltage rating, dielectric material, temperature behavior, and polarity when applicable. A capacitor marked 104may look simple, but the same nominal value can behave very differently as C0G, X7R, Y5V, film, tantalum, or electrolytic technology.
For quick checks, use the Capacitor Code Calculator. This guide explains the decoding method so the calculator output is easier to understand and easier to verify in real hardware.
Capacitor Value Units
Small capacitor codes are normally decoded in picofarads. Designers often convert the result to nanofarads or microfarads because schematics, bills of material, and datasheets may use different unit conventions for the same physical value.
Formula reference
Capacitance unit conversion
1 nF = 1,000 pF1 µF = 1,000 nF1 µF = 1,000,000 pFVariable definitions
- pF
- picofarad, common base unit for three-digit capacitor codes
- nF
- nanofarad, often used for small filters and coupling capacitors
- µF
- microfarad, often used for bypass, bulk, and electrolytic capacitors
| Value | Equivalent pF | Equivalent nF | Equivalent µF |
|---|---|---|---|
| 1 nF | 1,000 pF | 1 nF | 0.001 µF |
| 10 nF | 10,000 pF | 10 nF | 0.01 µF |
| 100 nF | 100,000 pF | 100 nF | 0.1 µF |
| 1 µF | 1,000,000 pF | 1,000 nF | 1 µF |
Three-Digit Capacitor Codes
The common three-digit EIA pattern works like a resistor code, but the decoded capacitor value is normally in picofarads. The first digit and second digit form the significant number. The third digit tells how many zeros to add.
| Marking | Decoded value | pF | nF | µF | Notes |
|---|---|---|---|---|---|
| 101 | 100 pF | 100 | 0.1 | 0 | The first two digits are significant figures and the third digit is the pF multiplier. |
| 102 | 1 nF | 1,000 | 1 | 0.001 | The code 102 means 10 x 10^2 pF, equal to 1000 pF or 1 nF. |
| 103 | 10 nF | 10,000 | 10 | 0.01 | Often written as 0.01 uF on schematics. |
| 104 | 100 nF | 100,000 | 100 | 0.1 | One of the most common decoupling capacitor markings. |
| 105 | 1 uF | 1,000,000 | 1,000 | 1 | The code 105 means 10 x 10^5 pF, equal to 1 uF. |
| 221 | 220 pF | 220 | 0.22 | 0 | Common value for filters, compensation, and coupling at high impedance nodes. |
| 472 | 4.7 nF | 4,700 | 4.7 | 0.005 | Standard preferred capacitor value in ceramic and film families. |
What Does 104 Mean?
The marking 104 is one of the most common capacitor markings. It is often used on 100 nF ceramic decoupling capacitors. The value is not 104 µF and not 104 nF. It follows the three-digit pF rule.
Formula reference
104 capacitor code
104 = 10 × 10^4 pF104 = 100,000 pF104 = 100 nF104 = 0.1 µFVariable definitions
- 10
- first two significant digits
- 10^4
- multiplier from the third digit
- The decoded result is first expressed in picofarads
In practical design, a 104 capacitor is often selected for local bypassing, but the marking alone does not confirm dielectric, DC bias behavior, rated voltage, tolerance, or package reliability.
Two-Digit and Direct Markings
Some small capacitors print the value directly. For example, markings such as 10, 22, 33, or 47 may indicate direct picofarad values. The shared capacitor code data includes common direct markings where they are useful for engineering examples.
Larger electrolytic capacitors usually print values such as 10 µF, 47 µF, or 100 µF directly because the body has enough space. They may also print voltage rating, polarity, temperature rating, and series information. Other parts may use decimal markings, manufacturer codes, or package-specific shorthand, so direct visual identification should always be checked before production use.
Tolerance Codes
A letter after the numeric code may indicate tolerance. Common examples include J, K, M, and Z, but tolerance letters are not a complete part specification. Always check the datasheet when tolerance matters to timing, cutoff frequency, analog accuracy, or production yield.
| Suffix | Tolerance | Notes |
|---|---|---|
| B | ±0.1 pF | Absolute tolerance used for very small capacitance values. |
| C | ±0.25 pF | Absolute tolerance used for small ceramic capacitors. |
| D | ±0.5 pF | Absolute tolerance used for small capacitance values. |
| F | ±1% | Precision tolerance, often for stable dielectrics. |
| G | ±2% | Precision ceramic or film capacitor tolerance. |
| J | ±5% | Common capacitor tolerance marking. |
| K | ±10% | Very common ceramic capacitor tolerance marking. |
| M | ±20% | Common for ceramic, electrolytic, and tantalum capacitors. |
| Z | -20% / +80% | Wide tolerance marking often associated with high-K ceramics. |
Voltage Rating and Additional Markings
What the value code usually does not tell you
- Rated voltage and surge voltage margin
- Dielectric class and temperature behavior
- DC bias capacitance loss
- Polarity, date code, and manufacturer series
Where to verify the missing details
- Manufacturer datasheet and ordering code
- Package marking guide for that series
- Distributor parametric data
- LCR or capacitance measurement when parts are unknown
Polarized Capacitors
Electrolytic and tantalum capacitors are usually polarized. Aluminum electrolytic capacitors commonly mark the negative side with a stripe, while tantalum capacitors often mark the positive side. Reversing polarity can cause leakage, heating, venting, or catastrophic failure, so never rely on capacitance value alone when installing polarized capacitors.
Worked Examples
Marking 104
Decode the numeric part as 100 nF. The value is 100,000 pF, 100 nF, or 0.1 µF.
Tolerance: Depends on suffix or part family.
A very common ceramic decoupling value for digital IC power pins.
Marking 103
Decode the numeric part as 10 nF. The value is 10,000 pF, 10 nF, or 0.01 µF.
Tolerance: Depends on suffix or part family.
Useful for filtering, timing, and small signal coupling.
Marking 472
Decode the numeric part as 4.7 nF. The value is 4,700 pF, 4.7 nF, or 0.005 µF.
Tolerance: Depends on suffix or part family.
Often used in filters, coupling paths, and EMI-related networks.
Marking 221
Decode the numeric part as 220 pF. The value is 220 pF, 0.22 nF, or 0 µF.
Tolerance: Depends on suffix or part family.
Common around high-impedance analog nodes and compensation paths.
Marking 105
Decode the numeric part as 1 uF. The value is 1,000,000 pF, 1,000 nF, or 1 µF.
Tolerance: Depends on suffix or part family.
A common local bulk or bypass value when dielectric and voltage rating are suitable.
Marking 104K
Decode the numeric part as 100 nF. The value is 100,000 pF, 100 nF, or 0.1 µF.
Tolerance: ±10%.
The K suffix commonly indicates ±10%, but always confirm the datasheet for the part family.
Common Mistakes
Assuming every capacitor code is already in nF.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Forgetting that the common three-digit result is usually in pF.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Confusing 104 with 104 µF instead of 0.1 µF.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Ignoring tolerance letters such as J, K, M, or Z.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Using the value code without checking voltage rating.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Overlooking dielectric type in timing or precision filters.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Assuming all manufacturer markings follow one universal format.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Failing to verify polarized capacitor orientation.
Treat the marking as identification data, then verify the part against the circuit requirement, measurement, or datasheet.
Engineering Tips
Use the Capacitor Code Calculator for quick decoding.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Verify uncertain parts with an LCR meter when accuracy matters.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Check the datasheet before production use.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Confirm voltage derating, especially for ceramic and tantalum capacitors.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Confirm dielectric type for timing, filtering, and precision circuits.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Document unknown salvaged parts before reuse.
This helps avoid selecting a part that has the right nominal capacitance but the wrong real-world behavior.
Preferred Capacitor Values
Capacitors often follow preferred values such as E6, E12, and E24. These values make inventory and substitution easier, but tolerance, voltage, dielectric, package, and availability still decide whether a part is appropriate.
| Series | Values per decade | Typical tolerance | Typical applications |
|---|---|---|---|
| E6 | 6 | ±20% | Electrolytic capacitors, bulk capacitance, broad decoupling, low precision timing |
| E12 | 12 | ±10% | General-purpose ceramic, film, electrolytic, and timing capacitor selection |
| E24 | 24 | ±5% | Film capacitors, precision timing, analog filters, tolerance-sensitive selection |
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FAQ
What does 104 mean on a capacitor?
The marking 104 means 10 × 10^4 pF, which equals 100,000 pF, 100 nF, or 0.1 µF.
Are three-digit capacitor codes expressed in pF?
Yes, common EIA three-digit capacitor codes are decoded in picofarads. The first two digits are significant figures and the third digit is the multiplier.
What is the difference between 103 and 104?
103 means 10,000 pF, or 10 nF. 104 means 100,000 pF, or 100 nF. The last digit changes the multiplier by one decade.
How do I convert pF to nF and µF?
Divide picofarads by 1,000 to get nanofarads, and divide picofarads by 1,000,000 to get microfarads.
What does the letter K mean on a capacitor?
K commonly means ±10% tolerance, but tolerance markings can vary by capacitor family and manufacturer, so production designs should check the datasheet.
Do capacitor codes include voltage rating?
Usually no. Numeric value codes identify capacitance, but voltage rating, dielectric type, temperature class, and reliability details often require the package marking or datasheet.
How can I identify capacitor polarity?
Electrolytic capacitors usually mark the negative lead or stripe. Tantalum capacitors often mark the positive terminal. Always verify the package convention before installation.
Can I verify a capacitor value with a multimeter?
Some multimeters can measure capacitance, but an LCR meter is usually better for accuracy, frequency-dependent behavior, ESR, and small capacitor values.
Are all capacitor markings standardized?
No. Many ceramic and film capacitor codes follow common EIA patterns, but manufacturer-specific markings, voltage codes, date codes, and package limitations are common.
Why do some capacitors show the full value instead of a code?
Larger components, especially electrolytic capacitors, often have enough body area to print the capacitance, voltage rating, polarity, and temperature rating directly.