Capacitors
Capacitor Code Calculator
Type the code printed on a ceramic or film capacitor and get the capacitance in pF, nF and µF, plus the tolerance if a letter is included.
3-digit code, read in picofarads
Marking on the part
±5%
How ceramic capacitor codes work
Small ceramic and film capacitors carry a three-digit code that works exactly like the SMD resistor code, except that the result is always in picofarads. The first two digits are the significant figures and the third is the number of zeros.
104 is 10 followed by four zeros — 100,000 pF, which is 100 nF or 0.1 µF, the ubiquitous decoupling capacitor. 102 is 1,000 pF = 1 nF. 223 is 22,000 pF = 22 nF.
Values below 100 pF are usually printed directly: 22 means 22 pF, not 22 with no zeros — which happens to be the same thing. Below 10 pF you may see R-notation, where 1R5 means 1.5 pF.
European parts often use the alternative notation where the unit character replaces the decimal point: 4n7 is 4.7 nF, 100n is 100 nF, 2µ2 is 2.2 µF.
The tolerance letter
A letter after the digits gives the tolerance. Small-value capacitors use absolute tolerances in picofarads; larger ones use percentages.
| 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% |
Dielectric codes matter more than tolerance
The three-character dielectric code (C0G, X7R, Y5V and friends) tells you how the capacitance behaves over temperature — and, for Class 2 dielectrics, how badly it collapses under DC bias. That last effect is far larger than the printed tolerance and is the single most common surprise in ceramic capacitor selection.
- C0G / NP0 — Class 1. Within ±30 ppm/°C, essentially no DC bias effect, no ageing, no microphonics. Use for timing, filters, oscillators and anywhere the value must be predictable. Limited to small capacitances in a given package.
- X7R — Class 2. ±15% from −55 °C to +125 °C. Good general-purpose decoupling. Loses capacitance under DC bias — often 30–50% at rated voltage.
- X5R — like X7R but only to +85 °C. Common in higher-capacitance small packages.
- Y5V / Z5U — Class 2/3, +22%/−82% over temperature. Cheap and high-capacitance on paper; avoid for anything that has to work reliably.
DC bias derating, in practice
A 10 µF X5R in an 0805 package rated at 16 V can measure under 3 µF when you actually apply 12 V to it. Nothing is faulty — it is inherent to the ferroelectric ceramic. The fix is to over-specify: choose a voltage rating at least twice your working voltage, use a larger package where you can, and check the manufacturer's bias curve rather than the headline value. C0G parts do not suffer from this at all, which is why they are the only sensible choice in a timing circuit.
Voltage rating codes
Through-hole ceramics often print the voltage rating directly (50V, 2kV). Some use a letter-and-digit EIA code where, for instance, 1H means 50 V and 2A means 100 V. If a disc capacitor has no rating marked at all, treat it as a low-voltage part and check the datasheet before putting it anywhere near a mains-derived rail.
Frequently asked questions
What does 104 mean on a capacitor?
It is a 3-digit code read in picofarads: 10 followed by four zeros = 100,000 pF = 100 nF = 0.1 µF. This is the most common decoupling capacitor value in electronics.
What is 104 in microfarads?
0.1 µF. The code gives 100,000 pF; divide by one million to get microfarads.
What does the letter after a capacitor code mean?
It is the tolerance. J is ±5%, K is ±10%, M is ±20%. On small-value parts the tolerance is absolute instead: B is ±0.1 pF, C is ±0.25 pF, D is ±0.5 pF. So 223K is 22 nF ±10%.
What is the difference between X7R and C0G capacitors?
C0G (also called NP0) is a Class 1 dielectric — stable within about ±30 ppm/°C, with no meaningful DC bias effect. X7R is Class 2 — ±15% over temperature and it can lose 30–50% of its capacitance under DC bias. Use C0G for timing and filters, X7R for general decoupling.
Why does my 10 µF capacitor measure much less in circuit?
DC bias derating. Class 2 ceramics (X5R, X7R, Y5V) lose capacitance as the applied DC voltage rises — a 16 V rated 10 µF part can fall below 3 µF at 12 V. Choose a voltage rating at least twice your working voltage, or a larger package.
What does 4n7 mean?
4.7 nF, written in the European style where the unit letter replaces the decimal point. The same convention gives 100n for 100 nF and 2µ2 for 2.2 µF. It exists because a printed decimal point is easy to lose on a small part.