Capacitance codes identify capacitor values when the package is too small for a full value to be printed. The most common three-digit code expresses capacitance in picofarads, but markings vary by capacitor type, size and manufacturer. Always compare the code with the datasheet and package.
Understand the base unit
The three-digit system normally uses picofarads as the base unit. One nanofarad equals 1,000 picofarads, and one microfarad equals 1,000,000 picofarads. Converting the decoded value to nF or µF often makes the number easier to recognize.
Decode a three-digit capacitance code
The first two digits are significant figures. The third digit is the number of zeros to add in picofarads. For example, 104 means 10 followed by four zeros, or 100,000 pF. That equals 100 nF or 0.1 µF.
| Code | Value in pF | Converted value |
|---|---|---|
| 100 | 10 pF | 10 pF |
| 221 | 220 pF | 220 pF |
| 102 | 1,000 pF | 1 nF |
| 472 | 4,700 pF | 4.7 nF |
| 103 | 10,000 pF | 10 nF |
| 104 | 100,000 pF | 100 nF or 0.1 µF |
| 105 | 1,000,000 pF | 1 µF |
Read codes that include a decimal marker
Some markings use R as a decimal point. A code such as 4R7 can indicate 4.7 in the manufacturer’s stated unit. The unit is not universal across every package, so confirm the series datasheet before replacing the part.
Interpret tolerance letters
A letter may follow the value code to show capacitance tolerance. Common examples include J for ±5%, K for ±10% and M for ±20%. Precision and RF capacitor series may use additional letters with tighter or asymmetric tolerances. Use the exact datasheet table because the same character can have a different role in another marking system.
Do not confuse voltage with capacitance
Voltage rating may be printed separately, encoded by a letter or omitted from very small surface-mount parts. It cannot be calculated from the three-digit capacitance code. A physically similar capacitor can have a different voltage rating, dielectric and temperature behavior.
Account for dielectric and temperature behavior
Ceramic capacitors with the same nominal capacitance can behave differently under DC bias and temperature. Check dielectric class, rated voltage, package size and the manufacturer’s capacitance-change curves. For timing, filtering and precision circuits, tolerance alone may not describe the effective in-circuit value.
Recognize polarized capacitor markings
Electrolytic and tantalum capacitors normally show polarity, but the symbol convention differs. Aluminum electrolytics often mark the negative terminal, while molded tantalum parts commonly mark the positive terminal. Verify the datasheet and board polarity before installation.
Check unmarked SMD capacitors
Many small multilayer ceramic capacitors carry no readable value. Identify them from the BOM, reel label, storage location or measurement. Capacitance measurement alone may not reveal voltage rating, dielectric, tolerance or qualification grade.
Capacitor identification checklist
- Read the complete body or reel marking
- Decode the value in the correct base unit
- Convert pF, nF and µF carefully
- Identify tolerance, voltage and dielectric separately
- Confirm polarity for polarized devices
- Match package dimensions and terminal style
- Verify the exact manufacturer series and datasheet
For component options, review our passive component sourcing page. If a marking is unclear, send Informic the code, dimensions and clear photos.
