Capacitor Code Calculator
Decode 3-digit ceramic / film codes (104, 222, 473) for THT and SMD parts. Covers MLCC, Tantalum, and Electrolytic SMD capacitors with polarity and identification guides.
Capacitance
100 nF
How ceramic / film capacitor codes work
THT Ceramic (disc) capacitor
THT Film capacitor
Ceramic and film capacitors use a 3-digit code where the first two digits are significant figures and the third is the power-of-ten multiplier, with the base unit in picofarads (pF). So 104 = 10 × 10⁴ pF = 100 nF = 0.1 µF.
Tolerance and voltage codes
- J = ±5 %, K = ±10 %, M = ±20 %
- Voltage codes (EIA-198): A=10 V, B=12.5 V, C=16 V, D=20 V, E=25 V, F=32 V, G=40 V, H=50 V
Quick experiments
- Decode the most common capacitor in existence. Enter
104. That is 10 followed by four zeros in picofarads — 100 000 pF, which is 100 nF, which is the 0.1 µF decoupling capacitor sitting next to almost every IC ever made. - Small values skip the multiplier. Try
470. The trailing zero is a multiplier of 100, so this is 47 pF — not 470 pF. This trips up almost everyone once. - Add a tolerance letter.
104Kis 100 nF at ±10 %,104Jthe same value at ±5 %. On ceramics the letter is often the only tolerance marking present. - Compare against a printed value. Larger film and electrolytic parts skip codes entirely and print something like
0.22 µFor10 µF 25 V. The code system exists because a 0603 ceramic has no room for that.
Capacitor codes — reference
The three-digit code is read in picofarads. The first two digits are significant, the third is the number of zeros to append. So 223 is 22 followed by three zeros = 22 000 pF = 22 nF. Converting to the unit you actually want is usually the harder half: 1 000 pF = 1 nF, and 1 000 nF = 1 µF.
Tolerance letters
A letter after the digits gives tolerance: J is ±5 %, K is ±10 %, M is ±20 %, and Z is the notably asymmetric −20 % / +80 % you find on cheap high-value ceramics. That last one is fine for bulk decoupling and useless for a filter.
The dielectric matters more than the code
A ceramic capacitor's three-character dielectric code describes how much its value drifts. C0G / NP0 is stable to within ±30 ppm/°C — use it for oscillators, filters and timing. X7R holds ±15 % from −55 to +125 °C — fine for decoupling. Y5V can lose most of its capacitance at temperature extremes, so a nominal 1 µF Y5V part may behave like a fraction of that in a warm enclosure.
DC bias derating — the invisible trap
High-value ceramics lose capacitance under applied DC voltage, and the effect is large: a 10 µF X5R rated 16 V can measure closer to 3 µF when actually run at 12 V. This is not in the code and not in the tolerance letter — it is in the manufacturer's bias curve. If a supply rail is unstable despite "enough" capacitance, this is a common culprit.
Voltage rating
The rating is a maximum, not an operating point. Derating to roughly half the rated voltage is normal practice, and mandatory for electrolytics, where running near the limit shortens life sharply.
Common mistakes
Reading the 3-digit code as a value in microfarads.
The scheme is in picofarads. 104 is 100 000 pF = 100 nF = 0.1 µF, not 104 µF — a factor of a million, and the single most common capacitor mistake.
Assuming the marked value is what you get in circuit.
Class 2 ceramics (X7R, Y5V) lose capacitance under DC bias, sometimes over half at rated voltage. Derate by choosing a higher voltage rating or a larger package.
Ignoring the dielectric code.
C0G/NP0 is stable; X7R drifts with temperature and bias; Y5V is worse still. Using Y5V in a filter or timing circuit gives a corner frequency that wanders with temperature.
Choosing a voltage rating equal to the working voltage.
Rated voltage is a maximum, not an operating point. Allow at least 2× headroom, more for ceramics where capacitance falls as bias approaches the rating.
Fitting an electrolytic backwards.
Polarised capacitors mark the negative lead with a stripe, and the longer lead is positive. Reversed, they heat, vent and can burst — unlike ceramics, which are not polarised.
Frequently asked questions
How do I read a 3-digit capacitor code?
The first two digits are significant figures and the third is the number of zeros, giving a value in picofarads. Code 104 means 10 followed by 4 zeros, which is 100000 pF, or 100 nF, or 0.1 uF.
Why are capacitors marked in picofarads?
The 3-digit scheme was designed around picofarads so common values need no decimal point. It is why the familiar 0.1 uF decoupling capacitor is stamped 104 rather than anything resembling its microfarad value.
What does the letter after the capacitor code mean?
It is the tolerance. J is 5 percent, K is 10 percent and M is 20 percent. On class 1 ceramics letters such as C or D denote tighter tolerances in absolute picofarads.
What is the difference between X7R and C0G capacitors?
C0G, also called NP0, is a class 1 dielectric that is stable with temperature and voltage but limited in capacitance. X7R is class 2, offering far more capacitance per package while losing a substantial fraction of its value under DC bias.
Why does my capacitor measure lower than its marked value?
Class 2 ceramics such as X7R and Y5V lose capacitance under applied DC voltage, sometimes more than half at rated voltage, and they also drift with temperature and age. The marked value applies only at the datasheet's test conditions.
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