270 capacitor value
27 pF
27 pF · 0.027 nF · 0.000027 µF
| Marked code | 270 |
| Picofarads | 27 pF |
| Nanofarads | 0.027 nF |
| Microfarads | 0.000027 µF |
| Farads | 2.70e-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:
27 × 100 = 27 pF
So 270 is 27 followed by 0 zeros: 27 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 270 is stocked as 0.000027 µF and the two numbers look nothing alike.
What 27 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 27 pF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 117.89 MΩ |
| 1 kHz — audio | 5.89 MΩ |
| 100 kHz — switching | 58.95 kΩ |
| 10 MHz — RF | 589.46 Ω |
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 270K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 27 pF means |
|---|---|---|
270J | ±5% | 25.65 pF to 28.35 pF |
270K | ±10% | 24.3 pF to 29.7 pF |
270M | ±20% | 21.6 pF to 32.4 pF |
270Z | +80% / −20% | 21.6 pF to 48.6 pF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 270Z can legitimately be anything from 21.6 pF to 48.6 pF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 27 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 270 capacitor?
27 pF — 27 pF · 0.027 nF · 0.000027 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 270 is 27 followed by 0 zeros = 27 pF.
What is a 270 capacitor in µF?
0.000027 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 27 pF, 0.027 nF and 0.000027 µF are the same capacitor written three ways.
What does the letter after 270 mean?
Tolerance. 270K is ±10%, 270J is ±5% and 270M is ±20% — so a 270K is anywhere from 24.3 pF to 29.7 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 270 capacitor at 1 kHz?
5.89 MΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 58.95 kΩ at 100 kHz and 589.46 Ω at 10 MHz.
Nearby codes
- 330 capacitor — 33 pF
- 390 capacitor — 39 pF
- 470 capacitor — 47 pF
- 560 capacitor — 56 pF
- 680 capacitor — 68 pF
- 820 capacitor — 82 pF
- 101 capacitor — 100 pF
- 121 capacitor — 120 pF
- 151 capacitor — 150 pF
- 181 capacitor — 180 pF