How capacitor codes work
Small ceramic and film capacitors are too small for a full value, so manufacturers print a three-digit code in picofarads (pF):
- the first two digits are the significant figures;
- the third digit is the number of zeros to add (the power of ten);
- a letter after the code gives the tolerance.
Examples
| Code | Value |
|---|---|
| 101 | 100 pF |
| 102 | 1,000 pF = 1 nF |
| 103 | 10,000 pF = 10 nF |
| 104 | 100,000 pF = 100 nF = 0.1 µF |
| 105 | 1,000,000 pF = 1 µF |
| 223 | 22 nF |
| 473 | 47 nF |
| 229 | 2.2 pF (9 means × 0.1) |
A multiplier of 8 means × 0.01 and 9 means × 0.1, used for very small values. Multipliers 6 and 7 are not used.
Codes of one or two digits, such as “22” or “47”, are simply the value in picofarads.
Tolerance letters
| Letter | Tolerance |
|---|---|
| B | ±0.1 pF |
| C | ±0.25 pF |
| D | ±0.5 pF |
| F | ±1% |
| G | ±2% |
| J | ±5% |
| K | ±10% |
| M | ±20% |
| Z | +80% / −20% |
So 104K is 100 nF ±10%, anywhere from 90 to 110 nF. The B, C and D letters apply to small values below about 10 pF.
Voltage markings
A capacitor may also show a voltage rating, either directly (50V, 100V) or as a code such as 1H (50 V) or 2A (100 V) on some film capacitors. Always choose a rating comfortably above the circuit’s peak voltage.
Units refresher
- 1 µF = 1,000 nF = 1,000,000 pF
- 1 nF = 1,000 pF
Older schematics sometimes write “mF” or “MFD” meaning microfarads, and “mmF” or “MMFD” for picofarads (micro-microfarads).
Electrolytic capacitors
Aluminum electrolytic capacitors are large enough to print the value in µF directly, with the voltage and a stripe marking the negative lead. Tantalum capacitors often use the same three-digit code, but in pF, with the positive lead marked.
Ceramic capacitor types
The temperature code (C0G/NP0, X7R, Y5V) matters as much as the value: C0G is stable and precise, while X7R and especially Y5V lose much of their capacitance with temperature and applied DC voltage.