Capacitor Code Calculator
The marking on a small capacitor is a code, not a value: 104 is 100 nF, 4n7 is 4.7 nF, and the letter in 2u2 is the decimal point. Type what is printed on the part to get the value in pF, nF and µF, plus the tolerance when a letter follows the code.
Result
104 = 100 nF
| Quantity | Value |
|---|---|
| Capacitance | 100 nF |
| In picofarads | 100000 pF |
| In nanofarads | 100 nF |
| In microfarads | 0.1 µF |
Legacy markings, the classic trap. Old American parts use MFD and MMFD: MFD means microfarads, and MMFD means micro-microfarads, which are picofarads. A capacitor marked “0.1 MFD” is 100 nF; one marked “.001 MFD” is 1 nF. When in doubt, read it with this tool before soldering it in.
Common codes at a glance
| Code | Value | Where it shows up |
|---|---|---|
| 101 | 100 pF | Crystal loading, RF filters |
| 221 | 220 pF | Snubbers, RF |
| 471 | 470 pF | Filters, timing |
| 102 | 1 nF | Timing, high-frequency decoupling |
| 103 | 10 nF | Decoupling, filters |
| 104 | 100 nF | Everywhere: decoupling and bypass |
| 474 | 470 nF | Coupling, bulk support |
| 105 | 1 µF | Bulk decoupling, regulators |
| 225 | 2.2 µF | Bulk, small power supplies |
Tolerance letters
| Marking | Tolerance |
|---|---|
104C | ±0.25 pF |
104D | ±0.5 pF |
104F | ±1% |
104G | ±2% |
104H | ±3% |
104J | ±5% |
104K | ±10% |
104M | ±20% |
104P | 0 to +100% |
104S | +50 to −20% |
104Z | +80 to −20% |
Worked example
A part marked 104K: two significant digits (10) followed by four zeros gives 100,000 pF, which is 100 nF or 0.1 µF; the K says ±10%, the everyday tolerance grade. Open this example.
FAQ
Why is 104 equal to 100 nF?
The first two digits are the significant figures (10) and the third is the number of zeros added, in picofarads: 10 with four zeros = 100,000 pF. One nanofarad is 1,000 pF and one microfarad is 1,000 nF, so 100,000 pF = 100 nF = 0.1 µF.
What do MFD and MMFD mean on old capacitors?
MFD is microfarad (the µ was not printable), and MMFD is micro-microfarad, which means picofarad. A 0.1 MFD capacitor is 100 nF; a .001 MFD capacitor is 1 nF.
Which voltage rating do I need?
The printed voltage is the maximum DC working voltage. Pick at least 1.5 to 2 times your rail for ceramics: their capacitance falls as the applied voltage approaches the rating. Electrolytics also wear out faster when run near their limit.
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