225 capacitor value
2.2 µF
2,200,000 pF · 2200 nF · 2.2 µF
| Marked code | 225 |
| Picofarads | 2,200,000 pF |
| Nanofarads | 2200 nF |
| Microfarads | 2.2 µF |
| Farads | 2.20e-6 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:
22 × 105 = 2,200,000 pF
So 225 is 22 followed by 5 zeros: 2,200,000 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 225 is stocked as 2.2 µF and the two numbers look nothing alike.
What 2.2 µF 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 2.2 µF part covers several orders of magnitude:
| Frequency | Reactance |
|---|---|
| 50 Hz — mains | 1.45 kΩ |
| 1 kHz — audio | 72.34 Ω |
| 100 kHz — switching | 723.4 mΩ |
| 10 MHz — RF | 7.2 mΩ |
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 225K carries a tolerance letter. It is not part of the value:
| Letter | Tolerance | 2.2 µF means |
|---|---|---|
225J | ±5% | 2.09 µF to 2.31 µF |
225K | ±10% | 1.98 µF to 2.42 µF |
225M | ±20% | 1.76 µF to 2.64 µF |
225Z | +80% / −20% | 1.76 µF to 3.96 µF |
A Z is worth knowing about. +80%/−20% is a real tolerance on cheap high-permittivity ceramics, and it means a part marked 225Z can legitimately be anything from 1.76 µF to 3.96 µF. Those go in decoupling positions where only the rough size matters, never in a timing or filter position.
Where 2.2 µF turns up
Hundreds of nanofarads up to a microfarad is bulk decoupling and audio coupling where the low end has to survive. Ceramics this large have moved to multilayer construction, and the capacitance falls off sharply with applied voltage — a part marked 1 µF can measure half that with its rated voltage across it.
Frequently asked questions
What is the value of a 225 capacitor?
2.2 µF — 2,200,000 pF · 2200 nF · 2.2 µF. The first two digits are the value in picofarads and the third is how many zeros follow, so 225 is 22 followed by 5 zeros = 2,200,000 pF.
What is a 225 capacitor in µF?
2.2 µF. Going from picofarads to microfarads is six decimal places, which is where most of the confusion with these codes comes from — 2,200,000 pF, 2200 nF and 2.2 µF are the same capacitor written three ways.
What does the letter after 225 mean?
Tolerance. 225K is ±10%, 225J is ±5% and 225M is ±20% — so a 225K is anywhere from 1.98 µF to 2.42 µF 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 225 capacitor at 1 kHz?
72.34 Ω. Reactance is 1 ÷ (2πfC), so it falls as the frequency rises: the same part is 723.4 mΩ at 100 kHz and 7.2 mΩ at 10 MHz.
Nearby codes
- 275 capacitor — 2.7 µF
- 335 capacitor — 3.3 µF
- 395 capacitor — 3.9 µF
- 475 capacitor — 4.7 µF
- 565 capacitor — 5.6 µF
- 685 capacitor — 6.8 µF
- 825 capacitor — 8.2 µF
- 106 capacitor — 10 µF
- 126 capacitor — 12 µF
- 156 capacitor — 15 µF