Capacitor markings decoder.
Three-digit codes, tolerance letters, microfarad/nanofarad/picofarad — every common capacitor marking decoded. The companion to the resistor color codes sheet.
The chart
| Marking format | Example | Decoded value | Where you'll see it |
|---|---|---|---|
| Direct (with units) | 100 µF, 0.1 µF, 4n7 | Reads exactly as printed. '4n7' = 4.7 nF (European notation: position of unit letter is the decimal point). | Electrolytic, larger film, datasheet specs |
| 3-digit code (pF) | 104 | 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF | Ceramic disc, small film |
| 3-digit code (pF) | 473 | 47 × 10³ pF = 47,000 pF = 47 nF = 0.047 µF | Ceramic disc |
| 3-digit code (pF) | 222 | 22 × 10² pF = 2,200 pF = 2.2 nF | Ceramic disc |
| 3-digit + tolerance letter | 104K | 100 nF ±10% | Most common ceramic capacitor format |
| 3-digit + tolerance letter | 472J | 4.7 nF ±5% | Tighter-tolerance ceramic |
| 4-digit (precision pF) | 1002 | 100 × 10² pF = 10,000 pF = 10 nF | Precision ceramic / NP0 |
| 4-digit (precision pF) | 4992 | 499 × 10² pF = 49.9 nF | Precision tolerance class |
| µF marked directly | .1, .47, 1, 4.7, 10, 100, 470 | Value in microfarads — usually electrolytic. | Electrolytic, large film |
| nF marked directly | 100n, 220n | 100 nF = 0.1 µF, 220 nF | European film capacitors |
| Voltage rating | 100V, 25V, 6.3V | DC voltage rating (always shown alongside capacitance) | Critical for any application |
| Tolerance code letters | B = ±0.1 pF, F = ±1%, J = ±5%, K = ±10%, M = ±20%, Z = +80/−20% | — | Reading capacitor tolerance |
| Temp coefficient (ceramic) | NP0/C0G, X7R, Y5V | NP0 = best (low drift), X7R = mid, Y5V = worst (high drift but cheap) | All ceramic capacitors |
| Polarity (electrolytic) | Stripe on case, − terminal | Reversed polarity destroys electrolytic caps quickly | Always observe orientation |
How the 3-digit code works. First two digits = the significant figures, third digit = the multiplier (number of zeros). Result is always in picofarads. So '104' = 10 followed by 4 zeros = 100,000 pF = 100 nF = 0.1 µF. The 'KP' or 'K' suffix is the tolerance (±10%).
Common applications
| Application | Typical capacitance | Type |
|---|---|---|
| Bypass cap on IC power pin | 100 nF (0.1 µF) | Ceramic X7R |
| Power supply bulk filter | 100-4700 µF | Aluminum electrolytic |
| Audio coupling (DC blocking) | 1-10 µF | Film or electrolytic (non-polar preferred) |
| RC low-pass filter | 1 nF to 1 µF | Film or ceramic (depending on frequency) |
| Crystal oscillator load | 10-30 pF | NP0/C0G ceramic |
| Snubber across switch | 10-100 nF | Film (X1/Y1 safety rated for mains) |
| Motor start (single phase) | 30-200 µF | Polypropylene film, motor-run rated |
| Switched-mode supply output | 100-1000 µF | Low-ESR aluminum or polymer |
| RF tuning | 5-100 pF | Variable or NP0 ceramic |
Common pitfalls
- 'µ' and 'u' mean the same thing. µF (microfarad) is often written as uF in ASCII-only contexts. Both equal 10⁻⁶ farads.
- nF is rarely printed on US caps. US capacitor catalogs traditionally use only pF (small) and µF (large). 100 nF is often listed as 0.1 µF or 100000 pF, but rarely as 100 nF. European catalogs use nF freely.
- The 4 in '4n7' is the integer and 7 is the decimal — the letter is the decimal point. So '4n7' = 4.7 nF. Common in European electronics. Similarly '2u2' = 2.2 µF, 'R47' = 0.47 Ω (for resistors, same convention).
- Electrolytic capacitors have polarity. Connecting them backwards causes them to fail violently (vented top, sometimes explosion). The stripe on the case marks the negative terminal. Non-polar 'NP' electrolytics exist for AC circuits.
- Capacitance drifts with temperature, voltage, age. Y5V ceramic loses 60-80% of capacitance at the edges of its temperature range. NP0/C0G is stable within 0.5%. Always check the dielectric type for precision work.
- '105' is not 105 pF. It's 10 × 10⁵ pF = 1 µF. The third digit is a multiplier, not part of the number. This trips up beginners constantly.
Common questions
What does '104' mean on a ceramic capacitor?
It's the EIA 3-digit code: first two digits are significant figures (10), third is the multiplier (×10⁴ pF). So 104 = 10 × 10⁴ pF = 100,000 pF = 100 nF = 0.1 µF. This is the most common decoupling capacitor value in electronics.
How do I tell µF from nF on a capacitor?
Modern small ceramic caps use 3-digit pF codes (104 = 100 nF). Larger electrolytic and tantalum caps print microfarad values directly (e.g. '10µF' or '47µF'). When in doubt: anything ≥ 1 µF is almost always electrolytic or tantalum and marked directly; anything in pF/nF is usually 3-digit coded ceramic.
What's a 'Y5V' or 'X7R' ceramic code?
Those are EIA dielectric class codes for ceramic capacitors. X7R means -55°C to +125°C operating range with ±15% capacitance variance — stable, predictable. Y5V means -30°C to +85°C with +22%/-82% — extreme variation, only suitable for non-critical coupling. NP0/C0G is the most stable (±30 ppm/°C); use it for precision timing.
Why doesn't my 'tolerance' letter J mean ±10%?
Capacitor tolerance letters are standardized: F = ±1%, G = ±2%, J = ±5%, K = ±10%, M = ±20%, Z = +80/-20%. People confuse them with resistor tolerance letters which use different codes. Always check whether the marking is per IEC 60062 (capacitor) or EIA RS-279 (resistor).
What's the difference between voltage rating and working voltage?
Voltage rating (sometimes called WVDC) is the maximum continuous DC voltage. Real circuits often have transient spikes — for reliability, derate to 50-70% of rated voltage. A 16V cap should see no more than ~10V continuous in a critical design. Aluminum electrolytics lose lifetime exponentially with voltage stress.
Sources
- Three-digit code: IEC 60062 — Marking codes for resistors and capacitors.
- Tolerance letters: EIA-198 — Standard for ceramic capacitor classes and tolerances.
- Temperature coefficients (ceramic): EIA-RS-198 (Class I — NP0, etc.) and EIA-RS-198 (Class II — X7R, Z5U, etc.).
Disclaimer. Capacitor specifications include not just capacitance but voltage rating, ESR, ripple current, and temperature behavior. For circuit design, consult the manufacturer's datasheet.