102 capacitor value
1 nF
1,000 pF · 1 nF · 0.001 µF
| Marked code | 102 |
| Picofarads | 1,000 pF |
| Nanofarads | 1 nF |
| Microfarads | 0.001 µF |
| Farads | 1.00e-9 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 × 102 = 1,000 pF
So 102 is 10 followed by 2 zeros: 1,000 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 102 is stocked as 0.001 µF and the two numbers look nothing alike.
What 1 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 1 nF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 3.18 MΩ |
| 1 kHz — audio | 159.15 kΩ |
| 100 kHz — switching | 1.59 kΩ |
| 10 MHz — RF | 15.92 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 102K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 1 nF means |
|---|---|---|
102J | ±5% | 950 pF to 1.05 nF |
102K | ±10% | 900 pF to 1.1 nF |
102M | ±20% | 800 pF to 1.2 nF |
102Z | +80% / −20% | 800 pF to 1.8 nF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 102Z can legitimately be anything from 800 pF to 1.8 nF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 1 nF turns up
Single-figure nanofarads is audio filtering and snubbing across switch contacts. It is also the range where a capacitor stops being a precision component and starts being a bypass, depending on the dielectric it is made from.
Frequently asked questions
What is the value of a 102 capacitor?
1 nF — 1,000 pF · 1 nF · 0.001 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 102 is 10 followed by 2 zeros = 1,000 pF.
What is a 102 capacitor in µF?
0.001 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 1,000 pF, 1 nF and 0.001 µF are the same capacitor written three ways.
What does the letter after 102 mean?
Tolerance. 102K is ±10%, 102J is ±5% and 102M is ±20% — so a 102K is anywhere from 900 pF to 1.1 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 102 capacitor at 1 kHz?
159.15 kΩ. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 1.59 kΩ at 100 kHz and 15.92 Ω at 10 MHz.
Nearby codes
- 122 capacitor — 1.2 nF
- 152 capacitor — 1.5 nF
- 182 capacitor — 1.8 nF
- 222 capacitor — 2.2 nF
- 272 capacitor — 2.7 nF
- 332 capacitor — 3.3 nF
- 392 capacitor — 3.9 nF
- 472 capacitor — 4.7 nF
- 562 capacitor — 5.6 nF
- 682 capacitor — 6.8 nF