Capacitor Code Calculator: How to Read 3-Digit, 4-Digit, and EIA-198 Markings

Decode every capacitor marking you will encounter — from the common 3-digit EIA code (104, 473) to 4-digit precision codes, R-notation, tolerance letters, and temperature coefficient designations — with worked examples you can verify using our calculator.

What Is a Capacitor Code and Why Does It Exist?

A capacitor code is the short numeric or alphanumeric marking printed on the body of a capacitor that encodes its capacitance value, and sometimes its tolerance and temperature coefficient. The system exists because most capacitors — especially ceramic discs, MLCCs (multi-layer ceramic chip capacitors), and film types — are physically too small to print their full value in readable text. A 0402 SMD capacitor (1.0 × 0.5 mm) has room for at most three characters, so "104" replaces "100 nF" or "0.1 µF".

The capacitor code system is standardized by the EIA-198-D specification ("Ceramic Dielectric Capacitors") in North America and by IEC 60062:2016 ("Marking codes for resistors and capacitors") internationally. Both standards define the same fundamental encoding rules: the result is always expressed in picofarads (pF), and the code digits follow a significand-plus-multiplier pattern identical to the resistor color code system. Every capacitor code calculator — including the Capacitor Code Calculator on this site — implements these rules.

Understanding how to read these codes is essential for anyone who works with electronics: selecting the wrong decoupling capacitor because you misread "103" (10 nF) as "104" (100 nF) can cause a circuit to oscillate or fail. This guide covers all the marking systems you will encounter, explains tolerance and temperature coefficient implications that most references skip, and walks through real worked examples you can verify with the Capacitor Code Calculator.

The 3-Digit EIA Code: The Most Common Capacitor Marking

The 3-digit code is by far the most widely used marking on ceramic and film capacitors. Per EIA-198-D and IEC 60062, the encoding rule is:

Where d₁d₂ are the first two digits (significant figures) and n is the third digit (the multiplier, i.e., the number of zeros to append). The result is always in picofarads.

Step-by-step decoding of 3-digit codes

1. Read the three digits from left to right on the capacitor body.
2. Take the first two digits as the significand (the base value).
3. Take the third digit as the multiplier exponent — it tells you how many zeros to append.
4. Multiply: C = significand × 10^multiplier pF.
5. Convert units as needed: 1,000 pF = 1 nF; 1,000,000 pF = 1 µF.

Worked Example 1: Decoding "104"

The most common ceramic capacitor code in electronics:

A capacitor marked "104" is 100 nF (0.1 µF). This is the standard bypass/decoupling capacitor value placed next to IC power pins. You can verify this with the Capacitor Code Calculator — enter "104" and confirm it returns 100 nF.

Worked Example 2: Decoding "473"

A "473" capacitor is 47 nF. This value is common in audio coupling circuits and EMI filter networks. At 1 kHz, a 47 nF capacitor has a reactance of X_C = 1/(2π × 1000 × 47×10^-9) = 3,386 Ω, making it suitable for coupling audio signals while blocking DC.

Worked Example 3: Decoding "220"

When the multiplier is 0, no zeros are appended. A "220" capacitor is 22 pF — a value commonly used in RF oscillator circuits (e.g., with a 10 MHz crystal, 22 pF loading capacitors match the crystal's specified load capacitance per IEC 60122-1).

Common 3-Digit Code Quick Reference

Memorize the pattern: codes 101 through 107 step through the "decade" values from 100 pF to 100 µF. This single pattern covers the majority of ceramic capacitors you will encounter on PCBs.

4-Digit Codes, R-Notation, and EIA-198: The Other Marking Systems

The 3-digit code covers most standard-tolerance ceramic capacitors, but three additional systems handle edge cases that 3 digits cannot.

4-Digit EIA Code: Higher Precision

When a capacitor needs three significant figures (for tighter tolerance or non-standard values), a 4-digit code is used. The first three digits are the significand and the fourth digit is the multiplier:

Worked Example 4: Decoding "4702"

While "473" also decodes to 47 nF, the 4-digit "4702" code specifies the value with three significant figures. This distinction matters for precision applications: a 47 nF capacitor with ±1% tolerance (F) requires the 4-digit code because the 3-digit code system cannot express values with three-digit significands. Film capacitors and C0G/NP0 ceramics with tolerances of ±1% or ±2% commonly use 4-digit codes per IEC 60062.

R-Notation: Values Below 10 pF

For capacitance values below 10 pF where a decimal point is needed, the letter R replaces the decimal point. This avoids misreading a tiny dot on small components:

R-notation values are common in RF circuits where small, stable capacitances are needed for impedance matching, tank circuits, and crystal oscillator load capacitors. A 4.7 pF C0G capacitor in a 315 MHz RF matching network, for example, must maintain its value within ±0.5 pF across temperature — only C0G/NP0 dielectric provides this stability.

EIA-198 Two-Character Code: The Smallest SMD Markings

When even three characters will not fit on the component (e.g., 0201 or 01005 SMD packages), the EIA-198 system uses just two characters: one letter (the significant figure) and one number (the multiplier). The letter maps to a value per a fixed table defined in EIA-198-D:

The multiplier digit follows the same power-of-ten rules as the 3-digit code but with different base positions. For example, A5 = 1.0 × 10⁵ pF = 100,000 pF = 100 nF. A capacitor code calculator that supports EIA-198 mode can decode these automatically — our Capacitor Code Calculator handles the standard 3-digit and 4-digit codes, and EIA-198 codes can be cross-referenced using the table above.

Tolerance Letters and Temperature Coefficients: What the Extra Characters Mean

After the numeric code, you will often see one or two additional characters on the capacitor body. These encode the tolerance (how much the actual value can deviate from the marked value) and the temperature coefficient (how the value changes with temperature). Both are critical for circuit performance, yet they are frequently ignored by beginners — sometimes with expensive consequences.

Tolerance Letters per IEC 60062

Worked Example 5: Decoding "104K" and "473J"

The K-tolerance 104K is the workhorse bypass capacitor on nearly every digital PCB. Its ±10% tolerance means the actual value could be anywhere from 90 nF to 110 nF at 25°C — acceptable for decoupling where the exact value is not critical, but unsuitable for a precision timing circuit. The J-tolerance 473J is a tighter grade, typically used in analog filter circuits where component value accuracy directly affects the filter's cutoff frequency.

Temperature Coefficients: C0G vs X7R vs Y5V

The temperature coefficient (TC) designation — printed on the capacitor body or listed in the datasheet — describes how the capacitance changes with temperature. This is defined in EIA RS-198 and IEC 60384-14. The three most common designations are:

The practical impact is enormous. A 100 nF Y5V capacitor at -30°C may provide only 18 nF of effective capacitance — less than one-fifth of its marked value. If this capacitor is part of an RC oscillator timing circuit, the frequency could shift by 5× or more. Per The Art of Electronics (Horowitz & Hill, 3rd ed., Cambridge University Press), "Class II and III ceramics are suitable only for bypass and decoupling applications where the exact capacitance value is unimportant." For any application where the capacitance value matters — oscillators, filters, sample-and-hold circuits, integrators — use C0G/NP0.

DC Bias Derating: The Hidden Factor in Ceramic Capacitor Codes

One of the least understood aspects of reading capacitor codes is that the marked value on a Class II ceramic (X7R, X5R, Y5V) is the value at zero DC bias and 25°C. When you apply a DC voltage across the capacitor, the effective capacitance decreases — sometimes dramatically. This is not a defect; it is an inherent property of the barium titanate dielectric used in Class II ceramics, documented in every manufacturer's datasheet per IEC 60384-14.

Per Murata's and TDK's published characteristic curves (the two largest MLCC manufacturers globally), a typical X5R 10 µF / 10 V capacitor in an 0805 package loses approximately 50% of its capacitance when biased to 5 V (50% of rated voltage). At 8 V (80% of rated), the loss can exceed 70%. This means a capacitor marked "106K" on your PCB may be providing only 3 µF of effective capacitance in-circuit.

Practical Derating Example

Consider a 4.7 µF / 10 V X5R capacitor (code 475K) used as the output filter capacitor on a 3.3 V LDO regulator:

• Marked value: 4.7 µF (from code 475)
• DC bias at 3.3 V (33% of rated): capacitance drops to approximately 3.5 µF per typical Murata curves
• At 85°C ambient: additional -15% from X5R temperature coefficient → 3.5 × 0.85 = 2.98 µF
• With ±10% tolerance: worst case = 2.98 × 0.90 = 2.68 µF

The effective capacitance in-circuit is 2.68 µF — only 57% of the 4.7 µF marked value. If the LDO requires a minimum 3.3 µF output capacitor for stability (per its datasheet), this part could cause oscillation. The solution: either use a higher-voltage-rated capacitor (4.7 µF / 25 V shows less DC bias loss), use a larger package (1206 vs 0805 has more dielectric volume and less bias effect), or oversize the nominal value by 2×.

C0G/NP0 capacitors do not exhibit DC bias derating — their dielectric (paraelectric titanium dioxide) does not have the ferroelectric nonlinearity of barium titanate. This is another reason to choose C0G for any application where the capacitance value matters.

Using the Capacitor Code Calculator: Workflow and Verification

The Capacitor Code Calculator supports both decode (code → value) and encode (value → code) modes. Here is the recommended workflow for each common task:

Decoding a marking from a physical component

1. Read the marking from the capacitor body. If there is a letter prefix (like "2A" in "2A473"), note it — it may be a voltage or temperature coefficient code.
2. Enter the numeric code (e.g., 473) into the calculator's decode mode.
3. Check the tolerance letter separately (e.g., K = ±10%) and note it for your BOM.
4. Cross-reference the dielectric type from the datasheet or the capacitor body marking (X7R, C0G, Y5V) to understand temperature and bias behavior.
5. For critical applications, verify the actual value with an LCR meter at the operating frequency and DC bias voltage.

Encoding a value for PCB marking or procurement

1. Enter the capacitance value in the calculator's encode mode (e.g., 100 nF).
2. Select the tolerance — this determines whether a 3-digit or 4-digit code is appropriate (±5% and tighter usually require 4-digit).
3. Record the generated code for your PCB silkscreen or BOM entry.

Worked Example 6: Full Marking Decode "2A473K"

A ceramic capacitor is marked 2A473K:

• 2A = voltage code (100 VDC per EIA voltage code table)
• 473 = capacitance code → 47 × 10³ pF = 47 nF = 0.047 µF
• K = tolerance → ±10%

Full specification: 47 nF, ±10%, 100 VDC. This is a common X7R capacitor used in DC-DC converter input filters and snubber circuits. Enter "473" in the Capacitor Code Calculator to confirm the 47 nF value.

Three Common Mistakes When Reading Capacitor Codes

Mistake 1: Treating All Digits as the Value

The most frequent error is reading "104" as 104 pF instead of 100,000 pF. The third digit is always the multiplier per EIA-198-D, never a value digit. A "104" capacitor is 100 nF, not 104 pF — a 1,000× difference. This mistake is especially common among beginners who are familiar with resistor color codes but have not yet internalized that the same significand-plus-multiplier system applies to capacitors. Use the Capacitor Code Calculator to verify every marking before populating a board.

Mistake 2: Using Y5V or Z5U in Timing Circuits

Y5V and Z5U ceramics can lose up to 82% of their capacitance over temperature. A 100 nF Y5V capacitor in an RC oscillator at -30°C may provide only 18 nF, shifting the frequency by 5.5×. If the oscillator drives a watchdog timer, the timeout could change from 10 ms to 55 ms — or vice versa. Always use C0G/NP0 for timing, oscillators, and any circuit where the capacitance value sets a frequency or time constant. See the RC Filter Calculator for an interactive demonstration of how capacitance affects filter cutoff frequency.

Mistake 3: Ignoring DC Bias Derating on Class II Ceramics

As covered in the DC bias section, a 10 µF X5R capacitor at 80% of its rated voltage may provide only 3 µF. Designing a power supply filter based on the marked value without accounting for bias derating is the single most common cause of LDO instability and switching converter ripple problems in production. Always check the manufacturer's DC bias curve (available on Murata's SimSurfing and TDK's SEAT tools) and derate accordingly.

Conclusion: Decode Every Marking, Verify Every Value

Reading capacitor codes is a fundamental skill that every electronics engineer, technician, and hobbyist needs — and the rules are simpler than they first appear. The 3-digit EIA code (significand × 10^multiplier pF) covers 90% of the capacitors you will encounter. The 4-digit code, R-notation, and EIA-198 system handle the remaining edge cases. Tolerance letters and temperature coefficient designations tell you whether the marked value can be trusted in your application — and the answer is "yes" for C0G/NP0, "with caveats" for X7R, and "almost never" for Y5V in any precision circuit.

The Capacitor Code Calculator handles decode and encode operations for the standard code systems. For selecting the correct dielectric type and package size, always consult the manufacturer's datasheet — Murata, TDK, Samsung Electro-Mechanics, and KEMET all provide detailed DC bias and temperature characteristic curves. For related component identification, use the Resistor Color Code Calculator and the SMD Resistor Code Calculator (for resistor markings that use the same EIA-198 system).

Key Takeaways

• 3-digit code: C = d₁d₂ × 10ⁿ pF (e.g., 104 = 100 nF)
• 4-digit code: C = d₁d₂d₃ × 10ⁿ pF (e.g., 4702 = 47 nF, precision)
• R-notation: R = decimal point (e.g., 4R7 = 4.7 pF)
• Tolerance: K = ±10% (most common), J = ±5%, M = ±20%
• C0G/NP0: Use for timing, oscillators, precision filters (most stable)
• X7R: Use for decoupling, general bypass (moderate stability)
• Y5V: Never use in timing circuits (up to 82% capacitance loss over temp)
• DC bias: Class II ceramics lose 20-80% capacitance at rated voltage — always check
• Verify with the calculator before placing parts on a board