479 capacitor value
4.7 pF
4.7 pF · 0.0047 nF · 0.000005 µF
| Marked code | 479 |
| Picofarads | 4.7 pF |
| Nanofarads | 0.0047 nF |
| Microfarads | 0.000005 µF |
| Farads | 4.70e-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:
47 × 0.1 = 4.7 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, 479 would be 47 × 109 = 47,000 µF, which is not a ceramic capacitor and not what is in your hand.
What 4.7 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 4.7 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 677.26 MΩ |
| 1 kHz — audio | 33.86 MΩ |
| 100 kHz — switching | 338.63 kΩ |
| 10 MHz — RF | 3.39 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 479K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 4.7 pF means |
|---|---|---|
479J | ±5% | 4.46 pF to 4.94 pF |
479K | ±10% | 4.23 pF to 5.17 pF |
479M | ±20% | 3.76 pF to 5.64 pF |
479Z | +80% / −20% | 3.76 pF to 8.46 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 479Z can legitimately be anything from 3.76 pF to 8.46 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 4.7 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 479 capacitor?
4.7 pF — 4.7 pF · 0.0047 nF · 0.000005 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 479 is 47 followed by a divide rather than a multiply: 47 × 0.1 = 4.7 pF.
What is a 479 capacitor in µF?
0.000005 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 4.7 pF, 0.0047 nF and 0.000005 µF are the same capacitor written three ways.
What does the letter after 479 mean?
Tolerance. 479K is ±10%, 479J is ±5% and 479M is ±20% — so a 479K is anywhere from 4.23 pF to 5.17 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 479 capacitor at 1 kHz?
33.86 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 338.63 kΩ at 100 kHz and 3.39 kΩ at 10 MHz.
Nearby codes
- 569 capacitor — 5.6 pF
- 689 capacitor — 6.8 pF
- 829 capacitor — 8.2 pF
- 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