Capacitor Code Calculator
Decode printed capacitor markings (like 104, 472K, 4R7, or 4n7) and generate a 3-digit EIA code from a capacitance value.
1) Decode a capacitor marking
2) Reverse lookup (value → 3-digit code)
Tip: Press Enter in either input field to run that calculation quickly.
How capacitor codes work
Many ceramic and film capacitors are too small to print full values like “0.1µF”. Instead, manufacturers use short codes. The most common format is a 3-digit number where the first two digits are significant figures and the third digit is the power-of-ten multiplier in pF (picofarads).
Example: 104 means 10 × 104 pF = 100,000 pF = 100 nF = 0.1 µF.
Most common code types
- 3-digit EIA: 102, 103, 104, 472
- 4-digit: Similar idea, but 3 significant digits + 1 multiplier digit
- R notation: 4R7 means 4.7 pF (R acts as decimal point)
- Inline unit notation: 4n7 means 4.7 nF
- Tolerance suffix: 104K adds tolerance letter K (±10%)
Tolerance letters (quick reference)
| 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 | -20% / +80% |
Worked examples
Example 1: 104
Take the first two digits: 10. Use the third digit (4) as multiplier: 10 × 104 = 100,000 pF. That is 100 nF or 0.1 µF.
Example 2: 472K
Base code: 472 → 47 × 102 = 4,700 pF = 4.7 nF. Tolerance K means ±10%.
Example 3: 4R7
R is the decimal marker. So this is simply 4.7 pF.
Example 4: 4n7
The letter n stands for nanofarads and also marks the decimal place. So 4n7 = 4.7 nF = 4,700 pF.
Why this matters in real builds
Picking the wrong capacitor value can shift filter cutoffs, destabilize oscillators, increase ripple, or prevent startup in power circuits. With a fast code calculator you can verify parts before soldering, avoid rework, and confidently substitute values when inventory is tight.
- Audio circuits: A small value error can noticeably shift tone controls.
- Power supplies: Capacitance and tolerance affect ripple and transient response.
- Timing circuits: RC time constants depend directly on capacitor value.
- RF designs: Low-pF accuracy and tolerance can be critical.
Important note about voltage rating and dielectric
This calculator focuses on capacitance code interpretation. In practical design you must also check:
- Voltage rating (must exceed circuit voltage with margin)
- Dielectric class (C0G/NP0, X7R, X5R, Y5V, etc.)
- Temperature behavior and DC bias effects (especially MLCCs)
- Package size and ESR/ESL requirements
A correct printed code is only one part of selecting the right capacitor.