104 capacitor value
100 nF
100,000 pF · 100 nF · 0.1 µF
| Marked code | 104 |
| Picofarads | 100,000 pF |
| Nanofarads | 100 nF |
| Microfarads | 0.1 µF |
| Farads | 1.00e-7 F |
Reading the code
The three digits are not a part number. The first two are the value in picofarads and the third says what to do with them:
10 × 104 = 100,000 pF
So 104 is 10 followed by 4 zeros: 100,000 pF. The code is always in picofarads even when the part is sold in microfarads, which is the whole difficulty with it — a capacitor marked 104 is stocked as 0.1 µF and the two numbers look nothing alike.
What 100 nF does at frequency
A capacitor's opposition to a signal is its reactance, 1 ÷ (2πfC), and it falls as the frequency rises. Over the range of frequencies a circuit can put across it, a 100 nF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 31.83 kΩ |
| 1 kHz — audio | 1.59 kΩ |
| 100 kHz — switching | 15.92 Ω |
| 10 MHz — RF | 159.2 mΩ |
Ten times the frequency is a tenth of the reactance, every time — which is why choosing a decoupling capacitor is really choosing the frequency band you want it to be low-impedance across, and why boards carry several sizes in parallel rather than one large one.
The letter after the number
A code like 104K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 100 nF means |
|---|---|---|
104J | ±5% | 95 nF to 105 nF |
104K | ±10% | 90 nF to 110 nF |
104M | ±20% | 80 nF to 120 nF |
104Z | +80% / −20% | 80 nF to 180 nF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 104Z can legitimately be anything from 80 nF to 180 nF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 100 nF turns up
A hundred nanofarads is the decoupling capacitor — the one that sits beside every integrated circuit on every board, holding the supply steady through the current spike each time the chip switches. If a board has one value on it more than any other, it is this one.
Frequently asked questions
What is the value of a 104 capacitor?
100 nF — 100,000 pF · 100 nF · 0.1 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 104 is 10 followed by 4 zeros = 100,000 pF.
What is a 104 capacitor in µF?
0.1 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 100,000 pF, 100 nF and 0.1 µF are the same capacitor written three ways.
What does the letter after 104 mean?
Tolerance. 104K is ±10%, 104J is ±5% and 104M is ±20% — so a 104K is anywhere from 90 nF to 110 nF and still in specification. A Z means +80%/−20%, which is not a mistake: some ceramic dielectrics really are that loose.
What is the impedance of a 104 capacitor at 1 kHz?
1.59 kΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 15.92 Ω at 100 kHz and 159.2 mΩ at 10 MHz.
Nearby codes
- 124 capacitor — 120 nF
- 154 capacitor — 150 nF
- 184 capacitor — 180 nF
- 224 capacitor — 220 nF
- 274 capacitor — 270 nF
- 334 capacitor — 330 nF
- 394 capacitor — 390 nF
- 474 capacitor — 470 nF
- 564 capacitor — 560 nF
- 684 capacitor — 680 nF