Capacitor Code Calculator
Decode the markings on a capacitor into pF, nF and µF — with tolerance, reactance and combinations.
The Capacitor Code Calculator runs entirely in your browser. Markings and values you enter are decoded on your device and never uploaded.
Open the Resistor Color Code Calculator
About Capacitor Code Calculator
A small ceramic or film capacitor has no room to print its value, so it carries a three-digit code in picofarads: two significant figures and a power-of-ten multiplier. That is why the ubiquitous 0.1 µF decoupling capacitor is stamped 104 — ten times ten to the fourth picofarads. European parts use a different convention entirely, putting the unit letter where the decimal point goes, so 4n7 is 4.7 nF, and a trailing letter on either style gives the tolerance. This calculator reads all of them, converts between the three units everyone quotes, and works out the reactance, RC corner frequency and combined value that the part is usually being chosen for.
Features
- Decodes three- and four-digit EIA codes, including the 8 and 9 multipliers
- Reads European markings such as 4n7, 2p2 and 1u5
- Handles bare picofarad numbers and decimal microfarad markings
- Tolerance letters decoded to a percentage and an actual value range
- Converts between pF, nF and µF at once
- Encodes a value back into the code printed on the part
- Reactance at a frequency and the RC corner frequency with a resistor
- Series and parallel totals for two capacitors
How to use the Capacitor Code Calculator
- Type the marking exactly as it appears on the part
- Read the value in picofarads, nanofarads and microfarads
- Check the tolerance range if the code ends with a letter
- Add a frequency or a resistor to see reactance and corner frequency
Example
Input
104K
Output
100 nF (0.1 µF) · 100,000 pF
Tolerance ±10% → 90–110 nF
Two significant figures and a multiplier: 10 × 10⁴ pF. The K is a tolerance letter, not a kilo prefix.
Common errors & troubleshooting
- The K in 104K is read as kilo. — It is the tolerance code for ±10 per cent. Capacitor codes never use SI prefixes as suffixes — J is ±5 per cent, K is ±10, M is ±20.
- A code like 479 decodes to a huge value. — The multipliers 8 and 9 mean ×0.01 and ×0.1, not ×10⁸ and ×10⁹. So 479 is 4.7 pF, not 47 gigafarads — a convention that exists purely to mark very small values in the same three digits.
- A decimal marking is read as picofarads. — A marking such as .01 or 0.47 is microfarads by convention, which is why .01 is 10 nF rather than a hundredth of a picofarad.
Frequently asked questions
- What does a 104 capacitor mean?
- 100 nanofarads, or 0.1 µF. The first two digits are significant figures and the third is the number of zeros to add, all in picofarads: 10 followed by four zeros is 100,000 pF.
- How do I read capacitor codes?
- Three digits are two significant figures plus a power-of-ten multiplier in picofarads. A letter after them is the tolerance. European markings put the unit letter where the decimal point goes, so 4n7 means 4.7 nF.
- What do the letters J, K and M mean on a capacitor?
- Tolerance. J is ±5 per cent, K is ±10 and M is ±20, with F and G marking the tighter ±1 and ±2 parts. B, C and D give absolute tolerances in picofarads for very small values.
- How do I convert nF to µF and pF?
- One microfarad is 1,000 nanofarads is 1,000,000 picofarads. So 100 nF is 0.1 µF and 100,000 pF — all three are shown at once above.
- How do capacitors add in series and parallel?
- The opposite way to resistors. In parallel they simply add; in series the reciprocals add, so two equal capacitors in series give half the value of one.
Related tools
All ArrayKit tools