100 capacitor value
10 pF
10 pF · 0.01 nF · 0.00001 µF
| Marked code | 100 |
| Picofarads | 10 pF |
| Nanofarads | 0.01 nF |
| Microfarads | 0.00001 µF |
| Farads | 1.00e-11 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 × 100 = 10 pF
So 100 is 10 followed by 0 zeros: 10 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 100 is stocked as 0.00001 µF and the two numbers look nothing alike.
What 10 pF 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 10 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 318.31 MΩ |
| 1 kHz — audio | 15.92 MΩ |
| 100 kHz — switching | 159.15 kΩ |
| 10 MHz — RF | 1.59 kΩ |
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 100K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 10 pF means |
|---|---|---|
100J | ±5% | 9.5 pF to 10.5 pF |
100K | ±10% | 9 pF to 11 pF |
100M | ±20% | 8 pF to 12 pF |
100Z | +80% / −20% | 8 pF to 18 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 100Z can legitimately be anything from 8 pF to 18 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 10 pF turns up
Tens of picofarads is the crystal load range: the two capacitors either side of a quartz crystal that set it oscillating at its marked frequency. Also RF tuning and the compensation capacitor round a fast op-amp.
Frequently asked questions
What is the value of a 100 capacitor?
10 pF — 10 pF · 0.01 nF · 0.00001 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 100 is 10 followed by 0 zeros = 10 pF.
What is a 100 capacitor in µF?
0.00001 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 10 pF, 0.01 nF and 0.00001 µF are the same capacitor written three ways.
What does the letter after 100 mean?
Tolerance. 100K is ±10%, 100J is ±5% and 100M is ±20% — so a 100K is anywhere from 9 pF to 11 pF 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 100 capacitor at 1 kHz?
15.92 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 159.15 kΩ at 100 kHz and 1.59 kΩ at 10 MHz.
Nearby codes
- 120 capacitor — 12 pF
- 150 capacitor — 15 pF
- 180 capacitor — 18 pF
- 220 capacitor — 22 pF
- 270 capacitor — 27 pF
- 330 capacitor — 33 pF
- 390 capacitor — 39 pF
- 470 capacitor — 47 pF
- 560 capacitor — 56 pF
- 680 capacitor — 68 pF