Reading Capacitor Codes: 104, 4n7, 473K and the Rest
A capacitor a few millimetres wide can't fit "0.1 µF ±10%" on its body, so the value is printed as a short code. There are four notations in common use, and once you know the rule each one is unambiguous.
1. The three-digit EIA code (104, 223, 471)
The first two digits are significant figures. The third is a multiplier — the number of zeros to append — and the whole result is in picofarads (pF).
104 → 10, then 4 zeros → 100,000 pF → 100 nF → 0.1 µF
| Code | pF | nF | µF |
|---|---|---|---|
| 101 | 100 | 0.1 | 0.0001 |
| 223 | 22,000 | 22 | 0.022 |
| 474 | 470,000 | 470 | 0.47 |
| 105 | 1,000,000 | 1,000 | 1 |
A third digit of 0 means "no zeros", not "×0": 100 is 10 pF, and 220 is 22 pF. A third digit of 8 or 9 is a special case meaning ×0.01 and ×0.1 respectively — rare, but 229 is 2.2 pF.
2. Letter-as-decimal shorthand (4n7, 2p2, 1µ5)
The unit letter sits where the decimal point would go, so there's nothing to misread:
4n7= 4.7 nF2p2= 2.2 pF1µ5(or1u5) = 1.5 µFn47= 0.47 nF = 470 pF
This is the norm on European film capacitors and in a lot of schematics.
3. Plain values (22, 4.7, 0.1)
A bare one- or two-digit number with no multiplier is picofarads: 22 is 22 pF. A number with a decimal point and no unit is usually microfarads on larger electrolytics: 4.7 printed on a can is 4.7 µF. Context (physical size, whether it's polarised) resolves the ambiguity.
4. The tolerance letter (473K, 104J)
A trailing letter states how far the real value may stray:
| Letter | Tolerance |
|---|---|
| D | ±0.5 pF |
| F | ±1% |
| G | ±2% |
| J | ±5% |
| K | ±10% |
| M | ±20% |
| Z | +80% / −20% |
So 473K is 47,000 pF = 47 nF at ±10%.
The codes you should not confuse with capacitance
- Voltage rating — often a separate digit-letter pair (
2A= 100 V,1H= 50 V) or just a plain number like "50V". Never exceed it in circuit. - Dielectric class — three characters like
C0G/NP0(very stable),X7R(moderate drift),Y5V/Z5U(large drift with temperature and voltage). This describes stability, not value, and matters for timing and filter circuits.
Sanity-checking a decode
Real capacitors follow standard value series (E6, E12), so common results are 10, 15, 22, 33, 47, 68 × a power of ten. If your decode gives an oddball like 37 nF, re-read the code — you've probably swapped a digit or misjudged a worn marking.
The capacitor code decoder handles all four notations. For resistors, the parallel tool is the resistor color code (and its Ohm's law guide). To use the capacitor in a timing circuit, the RC time constant calculator.