How to use the capacitor code calculator
- Choose Code → value and type exactly what is printed on the capacitor — for example
104,473J,2A104K,4n7or104K 50V X7R. - Read the value in pF, nF and µF, the tolerance (if there is a letter) and the voltage rating (if it is in the code).
- To go the other way, choose Value → code, enter the capacitance, and optionally pick a tolerance and voltage code. You get the 3-digit code, the letter code (like
4n7) and the full marking.
Tap any row in the table of common codes to decode it instantly.
Formula
Small ceramic and film capacitors are too tiny to print "0.1 µF" on, so they use a 3-digit code. The first two digits are the value and the third digit is the number of zeros. The answer is always in picofarads (pF).
Some parts use a letter as the decimal point instead: 4n7 = 4.7 nF, 2µ2 = 2.2 µF, 4R7 or 4p7 = 4.7 pF.
Tolerance letters and voltage codes
| Letter | Tolerance | Letter | Tolerance |
|---|---|---|---|
| B | ±0.1 pF | J | ±5% |
| C | ±0.25 pF | K | ±10% |
| D | ±0.5 pF | M | ±20% |
| F | ±1% | Z | +80% / −20% |
| G | ±2% |
Common EIA voltage codes: 0J = 6.3 V, 1A = 10 V, 1C = 16 V, 1E = 25 V, 1H = 50 V, 2A = 100 V, 2E = 250 V, 2G = 400 V, 2J = 630 V.
B, C and D are absolute tolerances used on very small capacitors (about 10 pF and below). In the voltage code the digit is a power of ten and the letter gives the first figures — A = 1.0, C = 1.6, E = 2.5, H = 5.0, J = 6.3.
Ceramic dielectric codes (X7R, C0G…)
Multilayer ceramic capacitors often carry a second code for the material. C0G (NP0) is very stable and best for timing and filters. X7R and X5R change by up to ±15% over temperature and are fine for decoupling. Y5V and Z5U can lose more than half their value with temperature and DC voltage, so avoid them where the value matters. The calculator explains any of these if you type them after the code.
Common mistakes
- Reading the third digit as a number.
100is 10 pF, not 100 pF. A 100 pF capacitor is marked101. - Mixing up nF and µF. 0.1 µF and 100 nF are the same thing; 100 µF is a thousand times bigger and is almost always an electrolytic.
- Ignoring the voltage rating. A capacitor rated 50 V on a 230 V circuit will fail. If no voltage is printed, check the datasheet before using it above low-voltage hobby circuits.
- Confusing capacitor and resistor codes. Four-digit codes such as
1002belong to SMD resistors — use the SMD resistor code calculator for those, or the resistor colour code calculator for banded resistors.
What to do next
Once you know the value, put it to work: find how fast a capacitor charges with the RC time constant calculator, design a filter with the RC filter cutoff calculator, or build a blinker with the 555 timer calculator. New to capacitors? Start with capacitors explained for beginners, and find assorted capacitors in our electronics kits.
