Capacitor Code Calculator decodes 3-digit capacitor codes (e.g., 104, 223), letter tolerance, voltage rating, and EIA marking with formulas, examples, FAQs, and references.

Capacitor Code Calculator

What this calculator does

The Capacitor Code Calculator decodes 3-digit numeric codes and letter notations found on ceramic and film capacitors. It instantly provides the capacitance in picofarads, nanofarads, and microfarads along with the tolerance range.

Inputs explained

  • Code type: Choose between a 3-digit code (like 104) or a direct letter value (like 4n7).
  • Code: The printed text on the capacitor body.
  • Tolerance letter: The letter following the value (e.g., J, K, M) indicating allowed variance.
  • Voltage rating: (Optional) Enter the rated voltage if printed, used for estimating reactance at common frequencies.

How it works / Method

According to EIA-198 standards, the first two digits represent the significant figures and the third digit represents the number of zeros (multiplier) in picofarads (pF). Letters directly translate to nano or micro multipliers (e.g., 4n7 is 4.7 nF).

Formulas used

  • 3-digit code XYZ: Value = (XY) × 10^Z picofarads
  • Letter notation: 4n7 = 4.7 nF, 100n = 100 nF, 2µ2 = 2.2 µF
  • Conversion: 1 µF = 1,000 nF = 1,000,000 pF
  • Reactance (Xc) = 1 / (2πfC) Ω

Units: Capacitance in pF, nF, µF. Reactance in Ohms.

μF

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Formulas

3-DigitpF = (Digit1_2) * 10^(Digit3)
Conversion1 µF = 1000 nF = 10^6 pF
ReactanceXc = 1 / (2πfC)

Quick Reference: Common Codes

CodepFnFµF
1011000.10.0001
102100010.001
10310,000100.01
104100,0001000.1
1051,000,00010001.0
10610,000,0001000010.0

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Step-by-step example

Scenario: You find a ceramic capacitor marked "104K 50V".

Formula: Value = (XY) × 10^Z pF

  1. First two digits are 10.
  2. Third digit is 4 (meaning four zeros, or × 10,000).
  3. Value = 10 × 10,000 = 100,000 pF.
  4. Convert to nF: 100,000 / 1000 = 100 nF.
  5. Convert to µF: 100 / 1000 = 0.1 µF.
  6. Tolerance 'K' means ±10%.

Result: 0.1 µF ±10%, Rated 50V.

Use cases

  • Repairing electronics and identifying replacement parts.
  • Designing analog audio filters and oscillators.
  • Identifying small SMD ceramic capacitors that lack space for full printing.
  • Replacing failed power supply (PSU) filter caps.
  • Educational assignments and hobbyist breadboarding.

Assumptions & limitations

  • Assumes EIA-198 standard marking codes.
  • Does not account for voltage derating (ceramic capacitors lose capacitance under DC bias).
  • Assumes printed codes have not been altered or custom-printed by the manufacturer.
  • Consult manufacturer datasheets for exact dielectric properties (e.g., X7R, C0G).
  • Consult a licensed professional for safety-critical repairs, especially in high voltage equipment.

Sources & references

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Frequently Asked Questions

The 104 code is a three-digit shorthand. The first two digits are the value in picofarads, and the third is the number of zeros to add. So 104 means 10 followed by 4 zeros = 100,000 pF = 100 nF = 0.1 µF. This is the most common decoupling capacitor you see across MCU boards and small LED driver PCBs. Memorize 104 = 0.1 µF and 105 = 1 µF and you'll save serious time at the bench.

103 follows the same three-digit rule: 10 followed by 3 zeros = 10,000 pF. Convert to microfarads by dividing by 1,000,000, which gives 0.01 µF. In nF that's 10 nF. We see this value in noise filters, RC snubbers across relay contacts, and audio coupling. If you ever feel unsure, pull out a capacitance meter and verify — small ceramics are notorious for fading markings and mixed-up bins.

Picofarad to nanofarad: divide by 1,000. Nanofarad to microfarad: divide by 1,000 again. So 1,000 pF = 1 nF = 0.001 µF and 1,000,000 pF = 1,000 nF = 1 µF. Walking up: 47 pF stays 47 pF. 4,700 pF becomes 4.7 nF. 4,700,000 pF becomes 4.7 µF. I keep the conversion ladder taped near my workbench because this trip-up breaks more student projects than any other single error.

Those letters are tolerance codes, just like the colored bands on resistors. J = ±5%, K = ±10%, M = ±20%. You'll also see F = ±1% and G = ±2% on precision parts. So a capacitor marked 104K is 100 nF ±10%. For timing circuits like 555 oscillators or filters, never use M-class — the frequency drift will throw your design off. Stick with J or better when accuracy matters.

Read the body markings: a number tells you the value (using the three-digit code), a letter beside it gives tolerance, and a separate code or color marks the temperature characteristic (X7R, Y5V, NPO, etc.). For example, 104K Z5U means 100 nF ±10% with a wide temperature drift. The dielectric type matters in real installations — Y5V capacitors lose much of their value when warm, which has caused failures in summer in panel-mounted electronics.

Yes, exactly the same. 100 nF = 0.1 µF = 100,000 pF. The naming just shifts based on which decade the value lands in. Engineers in datasheets often write 0.1 µF, while schematic designers prefer 100 nF because it avoids decimal points. Both are correct, both refer to the same component. I encourage juniors to use nanofarads in their schematics to keep the numbers clean, but to read either form fluently.

Voltage rating is normally printed separately, not encoded in the same way as capacitance. You will see something like 50V, 100V, or 1KV stamped on the body. Some calculators allow you to enter the voltage label so the tool can flag mismatches. Always pick a capacitor rated at least 1.5 to 2 times your circuit voltage. We had a 25V capacitor pop on a 24V rail because of a switching spike — a 50V part would have survived.