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Capacitor Code Decoder

Decode 3-digit capacitor code (e.g., 104 = 100nF) to capacitance in pF, nF, and μF. Works with ceramic, film, and tantalum capacitor markings.

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Formula

C(pF)=(d1×10+d2)×10d3C(pF) = (d_1 \times 10 + d_2) \times 10^{d_3}
d1— First digit (hundreds)
d2— Second digit (tens)
d3— Third digit (multiplier exponent)
C— Capacitance (pF)

How It Works

This calculator decodes EIA capacitor marking codes for electronics engineers, technicians, and hobbyists working with ceramic, film, and other small capacitors. Per EIA-198-D (Ceramic Dielectric Capacitors — Classes I, II, III, and IV) and IEC 60062:2016 (Marking codes for resistors and capacitors), the 3-digit code represents capacitance in picofarads: first two digits are significant figures, third digit is the power-of-10 multiplier. Dielectric class definitions (C0G, X7R, Y5V) are standardized in EIA RS-198 and IEC 60384-14 (Fixed capacitors for use in electronic equipment — Ceramic dielectric capacitors). The Art of Electronics (Horowitz & Hill, 3rd ed., Cambridge University Press) Chapter 1 provides a practical reference for capacitor selection in circuit design. Example: 104 = 10 × 10^4 pF = 100,000 pF = 100 nF = 0.1 uF. Tolerance codes follow: J = ±5%, K = ±10%, M = ±20%, Z = +80%/-20% (electrolytics). Temperature coefficient codes per EIA RS-198: C0G/NP0 = ±30 ppm/C (most stable), X7R = ±15% over -55 to +125 C, Y5V = +22%/-82% (least stable). Understanding these codes is critical: using Y5V instead of C0G in a timing circuit causes 100% capacitance variation vs 0.3%.

Worked Example

Problem

A ceramic capacitor is marked '223K X7R'. Decode the value, tolerance, and calculate effective capacitance at 85 C with 50% DC bias applied.

Solution
  1. Decode value: 223 = 22 × 10^3 pF = 22,000 pF = 22 nF = 0.022 uF
  2. Tolerance 'K': ±10%, so range = 19.8 nF to 24.2 nF at 25 C, no bias
  3. X7R temperature coefficient: ±15% from -55 C to +125 C
  4. At 85 C worst case: 22 nF × 0.85 = 18.7 nF (within X7R spec)
  5. DC bias derating (typical X7R at 50% rated voltage): -30% capacitance
  6. Combined worst case: 22 nF × 0.90 (tolerance) × 0.85 (temp) × 0.70 (bias) = 11.8 nF
  7. Effective range: 11.8 nF to 24.2 nF (2× variation!) - critical for timing circuits
  8. Recommendation: use C0G for timing, or oversize X7R by 2× for filtering

Practical Tips

  • ✓Common codes memorized per EIA-198: 101 = 100 pF, 102 = 1 nF, 103 = 10 nF, 104 = 100 nF, 105 = 1 uF, 106 = 10 uF. Pattern: code XYZ = XY × 10^Z picofarads
  • ✓Dielectric selection per Murata/TDK guidelines: C0G/NP0 for timing, oscillators, filters (most stable); X7R for decoupling, general purpose (good balance); X5R/Y5V for bulk capacitance only (worst stability but highest capacitance density)
  • ✓Voltage derating per industry practice: use 50% of rated voltage for reliable operation. A 10V capacitor should see max 5V in circuit. This also reduces capacitance loss from DC bias effect

Common Mistakes

  • ✗Misinterpreting the third digit as part of the value - '104' means 10 × 10^4 pF = 100 nF, not 104 pF. The third digit is always the exponent/multiplier per EIA-198
  • ✗Ignoring temperature coefficient implications - X7R loses 15% at temperature extremes, Y5V loses up to 82%. A 100 nF Y5V capacitor may be only 18 nF at -30 C. Use C0G/NP0 for stable applications
  • ✗Not accounting for DC bias voltage derating - Class II ceramics (X7R, X5R) lose 20-80% capacitance at rated voltage per manufacturer curves. A 10 uF/10V X5R at 8V may only provide 3-4 uF effective

Frequently Asked Questions

Per EIA-198: first two digits (10) are significant figures, third digit (4) is the 10^n multiplier in picofarads. 104 = 10 × 10^4 pF = 100,000 pF = 100 nF = 0.1 uF. This is the most common decoupling capacitor value. Tolerance is typically ±10% (K) or ±20% (M) unless marked.
Per EIA RS-198: X7R means capacitance stays within ±15% from -55 C (X) to +125 C (7), with max change R = ±15%. C0G/NP0: ±30 ppm/C = 0.003%/C (best). X5R: ±15% from -55 to +85 C. Y5V: +22%/-82% from -30 to +85 C (worst). For a 100 nF X7R at 125 C: expect 85-115 nF.

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