829 capacitor value
8.2 pF
8.2 pF · 0.0082 nF · 0.000008 µF
| Marked code | 829 |
| Picofarads | 8.2 pF |
| Nanofarads | 0.0082 nF |
| Microfarads | 0.000008 µF |
| Farads | 8.20e-12 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:
82 × 0.1 = 8.2 pF
The last digit here is 9, which is one of the two exceptions. Eight and nine do not mean 10⁸ and 10⁹ — they mean × 0.01 and × 0.1, and they exist so that values below ten picofarads can be written in the same three characters. Read literally, 829 would be 82 × 109 = 82,000 µF, which is not a ceramic capacitor and not what is in your hand.
What 8.2 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 8.2 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 388.18 MΩ |
| 1 kHz — audio | 19.41 MΩ |
| 100 kHz — switching | 194.09 kΩ |
| 10 MHz — RF | 1.94 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 829K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 8.2 pF means |
|---|---|---|
829J | ±5% | 7.79 pF to 8.61 pF |
829K | ±10% | 7.38 pF to 9.02 pF |
829M | ±20% | 6.56 pF to 9.84 pF |
829Z | +80% / −20% | 6.56 pF to 14.76 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 829Z can legitimately be anything from 6.56 pF to 14.76 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 8.2 pF turns up
Values of a few picofarads are trimming and compensation parts — tuning a crystal oscillator onto frequency, flattening the response of a probe, neutralising stray capacitance in an RF stage. At this size the capacitance of the board traces either side of the part is a serious fraction of the part itself.
Frequently asked questions
What is the value of a 829 capacitor?
8.2 pF — 8.2 pF · 0.0082 nF · 0.000008 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 829 is 82 followed by a divide rather than a multiply: 82 × 0.1 = 8.2 pF.
What is a 829 capacitor in µF?
0.000008 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 8.2 pF, 0.0082 nF and 0.000008 µF are the same capacitor written three ways.
What does the letter after 829 mean?
Tolerance. 829K is ±10%, 829J is ±5% and 829M is ±20% — so a 829K is anywhere from 7.38 pF to 9.02 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 829 capacitor at 1 kHz?
19.41 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 194.09 kΩ at 100 kHz and 1.94 kΩ at 10 MHz.
Nearby codes
- 100 capacitor — 10 pF
- 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