Learn how to read capacitor codes — 3-digit EIA, tolerance letters, voltage codes, color bands, and SMD markings — with tables and worked examples for every type.

If you’ve ever picked up a ceramic disc capacitor and stared at the tiny “104” stamped on its face wondering what it actually means, you’re not alone. Knowing how to read capacitor codes is one of those fundamental skills that every PCB engineer, repair technician, and serious hobbyist needs to have locked in. It’s not difficult once the logic clicks — but the sheer variety of marking systems across different capacitor types and eras makes it easy to get confused.

This guide covers every major system you’ll encounter: the 3-digit EIA code used on most ceramic and film capacitors, the EIA-198 alphanumeric system on precision parts, the legacy color code still showing up on vintage boards, electrolytic and tantalum markings, and the tricky world of SMD capacitors that sometimes have no markings at all. With complete reference tables and worked examples throughout, this is the only capacitor code reference you’ll need bookmarked.

Why Learning How to Read Capacitor Codes Actually Matters

It might seem like a small thing, but misreading a capacitor code has real consequences. A 100nF decoupling cap misread as 100pF will let gigahertz-range noise sail straight through your supply rail. A 25V capacitor mistaken for a 250V part will fail silently under normal operating conditions. In repair work, pulling a part without correctly recording the value from the old component leads to sourcing the wrong replacement — and a circuit that fails in the same place all over again.

Understanding the coding also helps you read a BOM correctly, catch component substitution errors during board bring-up, and avoid the classic “this small SMD cap looks identical to that other small SMD cap” confusion during rework.

Understanding Capacitor Units First

Before decoding any marking, you need to be solid on capacitance units. All capacitor codes resolve to a value in picofarads (pF) as the base unit, because pF is the lowest common denominator across the range of components you’ll find in a typical design.

Unit	Symbol	Equivalent in pF	Common Usage
Microfarad	µF (or uF)	1,000,000 pF	Electrolytics, large ceramics, film caps
Nanofarad	nF	1,000 pF	Film caps, mid-range ceramics
Picofarad	pF	1 pF	Small ceramics, RF/timing circuits

The conversions you’ll use constantly: 0.1µF = 100nF = 100,000pF. 10nF = 0.01µF = 10,000pF. Getting comfortable with these three representations means any code you decode will make intuitive sense straight away.

Note: on older or larger electrolytic capacitors you may see the abbreviation MFD printed on the case. This stands for microfarad (µF), not megafarad — a legacy notation that’s increasingly misleading now that supercapacitors extend into the actual farad range.

How to Read the 3-Digit Capacitor Code (The Most Common System)

The 3-digit code is the one you’ll use most. It appears on ceramic disc capacitors, small polyester film caps, and most SMD ceramics that are large enough to carry markings. The logic is nearly identical to reading a resistor code.

The rule: The first two digits are the significant figures. The third digit is the multiplier — specifically, the number of zeros to add after the first two digits. The result is always in picofarads (pF).

3-Digit Code Worked Examples

Code on Cap	First Two Digits	Multiplier (3rd digit)	Result in pF	Converted Value
104	10	4 zeros	100,000 pF	0.1 µF
473	47	3 zeros	47,000 pF	47 nF
102	10	2 zeros	1,000 pF	1 nF
221	22	1 zero	220 pF	220 pF
470	47	0 zeros	47 pF	47 pF
682	68	2 zeros	6,800 pF	6.8 nF
331	33	1 zero	330 pF	330 pF

The most common mistake engineers make when first learning how to read capacitor codes is treating the third digit as a literal digit rather than a multiplier. A capacitor marked 104 is not 104 pF — it’s 10 followed by four zeros, which is 100,000 pF or 0.1µF. This single confusion causes more incorrect component orders than anything else.

Special Multiplier Values: 8 and 9

The EIA RS-198 standard includes two special-case multipliers that you’ll rarely see but should know about:

3rd Digit	Multiplier	Example	Result
8	× 0.01	478	47 × 0.01 = 0.47 pF
9	× 0.1	479	47 × 0.1 = 4.7 pF

These appear on very low-value capacitors where the normal code would produce a meaninglessly small number.

When You See Just Two Digits

If a capacitor has only a two-digit marking — say, 47 or 22 — read that number directly as picofarads. 47 = 47 pF. 22 = 22 pF. No multiplier involved.

The “R” Decimal Point Notation

For values below 10 pF where a decimal point is needed, the letter R substitutes for the decimal point. This follows the same convention used for resistors.

Code	Meaning
3R9	3.9 pF
1R5	1.5 pF
R47	0.47 pF
4R7	4.7 pF

If you see an R in a capacitor code, you’re dealing with a sub-10 pF value — typical in RF matching networks, oscillator load circuits, and antenna tuning.

How to Read Capacitor Tolerance Codes

The tolerance letter typically appears immediately after the 3-digit capacitance code. So a capacitor marked 104K is 0.1µF with 10% tolerance — not a 1040-something value.

EIA Tolerance Letter Codes

Letter	Tolerance	Typical Application
B	±0.1 pF	Precision NP0/C0G
C	±0.25 pF	Precision NP0/C0G
D	±0.5%	Precision timing
F	±1%	Precision timing/RF
G	±2%	Standard precision
J	±5%	General-purpose ceramic
K	±10%	Standard bypass/decoupling
M	±20%	Power supply filtering
Z	+80% / −20%	Bulk storage, supercaps

In practice, the two codes you’ll see most often on a production PCB are J (±5%) and K (±10%). The tighter tolerances (D, F, G) almost always appear on C0G/NP0 dielectric parts used in oscillators, filters, and timing circuits. The M and Z tolerances are typical on large electrolytic values where absolute accuracy is less critical than bulk capacitance.

How to Read EIA Voltage Codes on Capacitors

Voltage rating is critical — and it’s often the marking that gets skipped during a quick bench check. On larger capacitors it’s printed plainly in volts (e.g., 50V, 100V). On smaller ceramic and film types, a two-character voltage code may be used instead.

EIA DC Voltage Code Table

Code	Voltage Rating (DC)
1A	10V
1C	16V
1E	25V
1H	50V
1J	63V
2A	100V
2C	160V
2E	250V
2W	450V
2H	500V
3A	1000V

A capacitor marked 2A474J should therefore be decoded as: 2A = 100V rating, 474 = 470,000 pF = 0.47µF, J = ±5% tolerance.

How to Read MLCC Dielectric Codes: C0G, X7R, X5R and More

On ceramic capacitors, you’ll frequently see a three-character dielectric code alongside or instead of a voltage code. This tells you how stable the capacitance is over temperature — which is often more important than the nominal value for precision or timing applications.

Class I Dielectric Codes (EIA RS-198)

The three-character code works as: [significant figure of temperature coefficient] + [multiplier] + [tolerance in ppm/°C]

The most important Class I dielectric is C0G (also written NP0). C0G means a temperature coefficient of 0 ±30 ppm/°C across −55°C to +125°C. It is the gold standard for stable, predictable performance in filters, oscillators, and precision analog circuits.

Class II Dielectric Codes (EIA RS-198)

Code	Temperature Range	Max Capacitance Change	Typical Use
X7R	−55°C to +125°C	±15%	General purpose, decoupling
X5R	−55°C to +85°C	±15%	Consumer electronics
Y5V	−30°C to +85°C	+22% / −82%	Bulk bypass only
Z5U	+10°C to +85°C	+22% / −56%	Bulk bypass only

The X7R and X5R codes are the most commonly specified Class II dielectrics in modern PCB design. Y5V and Z5U have extremely wide capacitance variation over temperature and are unsuitable for any application where the capacitor value needs to stay predictable — but they allow very high capacitance in small packages, which is why they show up in low-cost consumer goods.

How to Read the EIA-198 Two-Character Code (Letter + Number)

This system is used on precision SMD capacitors and is less common than the 3-digit code, but you’ll encounter it on tight-tolerance parts. A letter represents the significant figures of the capacitance, and a number represents the multiplier (power of 10).

EIA-198 Letter-to-Value Table (Selected Values)

Letter	pF Value	Letter	pF Value
A	1.0	a	2.5
B	1.1	b	3.5
C	1.2	c	4.0
D	1.3	d	4.5
E	1.5	e	5.0
F	1.6	f	6.0
G	1.8	g	7.0
H	2.0	h	8.0
J	2.2	j	9.0
K	2.4	—	—

Example: A5 = 1.0 × 10⁵ = 100,000 pF = 0.1µF. The number after the letter is the exponent (power of 10), not a multiplier in the sense of “add this many zeros.” So the number 5 means ×100,000.

This system is explicitly used on the DigiKey SMD Capacitor Code Calculator and on precision component datasheets from manufacturers like Murata and TDK for their tightly-toleranced C0G parts.

How to Read Capacitor Color Codes (Legacy Systems)

Color codes on capacitors are largely obsolete — you’ll find them on components from the 1960s through the mid-1980s, particularly on polyester film, mica, and some polystyrene types. If you’re repairing vintage audio gear, old radio equipment, or industrial equipment from that era, knowing how to read capacitor color codes is genuinely useful.

Standard Capacitor Color Code Table

Color	Digit Value	Multiplier	Tolerance	Voltage (certain types)
Black	0	×1	±20%	—
Brown	1	×10	±1%	100V
Red	2	×100	±2%	250V
Orange	3	×1,000	±3%	—
Yellow	4	×10,000	±4%	400V
Green	5	×100,000	±5%	16V
Blue	6	×1,000,000	±6%	63V
Violet	7	—	±12.5%	—
Grey	8	×0.01	±30%	25V
White	9	×0.1	±10%	—
Gold	—	×0.1	±5%	—
Silver	—	×0.01	±10%	—

Reading order for a 5-band capacitor: Band 1 and 2 are the significant digits. Band 3 is the multiplier. Band 4 is tolerance. Band 5 is working voltage. Always start reading from the end that has bands closer together, or from the end with a wider first band.

Color code example: Brown, Black, Orange, Gold = 10 × 1,000 = 10,000 pF = 10nF, ±5% tolerance.

Mica Capacitor Dot Codes

Mica capacitors used a dot matrix system rather than bands. A black first dot identifies the component as mica. Dots 2, 3, and 4 give the capacitance value in pF using the same digit-digit-multiplier logic. Dot 5 is tolerance and dot 6 is voltage class. The dot numbering goes left-to-right on the top row and right-to-left on the bottom row — a peculiar scheme that trips up first-time readers.

How to Read Electrolytic Capacitor Markings

Electrolytic capacitors are generally large enough to print values directly — 470µF 35V, for example. There’s no code to decode. The key information to check on an electrolytic:

Marking	What to Check
Capacitance value (µF)	Confirm the value matches the BOM
Voltage rating (V)	Must exceed the maximum circuit voltage with margin
Temperature rating (°C)	85°C vs. 105°C matters for service life
Polarity stripe	The stripe or negative marking indicates the cathode (−) lead

The negative lead on a through-hole electrolytic is indicated by a stripe running down the body. On radial electrolytics the negative lead is also shorter. When in doubt, measure both leads with a DMM — the positive lead will show a higher forward diode-like reading when the positive probe is on it.

How to Read SMD Tantalum Capacitor Codes

SMD tantalum capacitors use a positive polarity indicator rather than negative — and this is one of the most common “gotcha” differences for engineers transitioning from through-hole work. The bar, stripe, or bevel on the tantalum package marks the positive (anode) terminal. This is the reverse convention from through-hole electrolytics, where the stripe marks negative.

Larger SMD tantalums often print value and voltage directly: 107 / 6.3V = 100µF at 6.3V (using 3-digit pF code: 10 × 10⁷ = 100,000,000 pF = 100µF). Smaller tantalums may use the EIA voltage letter code described above.

SMD Ceramic Capacitors: When There Are No Markings

This is the reality of modern PCB work. Surface-mount ceramic capacitors in 0402, 0201, and smaller packages frequently carry no markings whatsoever. The chips are too small to print legibly, and in automated assembly there’s no need since the pick-and-place machine reads the reel tape, not the component body. This means:

• The BOM and assembly drawing are your primary reference
• The component reel label carries the part number and value
• A good LCR meter or capacitance meter is essential for identifying unmarked parts during debug or rework
• Never measure a capacitor in-circuit for a definitive value — always measure it out-of-circuit

For 0603 and larger, markings may be present in the 3-digit or EIA-198 format described above. For anything smaller, check your BOM and datasheet first.

Complete Quick-Reference Decoding Guide

Use this as a one-page cheat sheet:

What You See	System	How to Decode
Three digits only (e.g., 104)	EIA 3-digit	First two = significant digits, third = add that many zeros, result in pF
Three digits + letter (e.g., 104K)	EIA 3-digit + tolerance	Decode capacitance first, then letter = tolerance
Letter-digit prefix + 3-digit (e.g., 2A104J)	EIA with voltage code	First two chars = voltage, next three = capacitance, final letter = tolerance
Letter + number (e.g., A5)	EIA-198	Letter = significant figure value (from table), number = power of 10
R in code (e.g., 3R9)	Decimal notation	R = decimal point, result in pF
5 color bands	Legacy color code	Band 1+2 = digits, Band 3 = multiplier, Band 4 = tolerance, Band 5 = voltage
Value + V directly printed	Non-coded	Read directly — typical on electrolytics and large film caps
No markings	Unmarked SMD	Check BOM, measure with LCR meter out-of-circuit

Useful Resources for Reading Capacitor Codes

These tools and references will accelerate your work with unfamiliar markings:

• DigiKey SMD Capacitor Code Calculator — Handles 3-digit EIA, 4-digit EIA, and EIA-198 codes; fast and reliable
• EEPower Capacitor Code Calculator — Interactive decoder for ceramic disc capacitor codes including tolerance
• Electronics Tutorials: Capacitor Colour Codes — Comprehensive legacy color code reference with worked examples
• Electronics Notes: Capacitor Markings and Codes — Covers all marking types including tantalum, electrolytic, film, and SMD
• iequalscdvdt.com Markings Reference — Detailed treatment of EIA vs IEC vs JIS systems with case codes for SMD packaging
• Knowles Capacitors: Dielectric Coding Guide — Deep reference on Class I and Class II temperature coefficient codes (C0G, X7R, X5R, etc.)
• ECIA EIA RS-198 Standard (PDF) — The primary standard document behind ceramic capacitor marking codes

Frequently Asked Questions About How to Read Capacitor Codes

Q1: A capacitor on my board is marked “104” — is that 104 picofarads?

No, this is the most common misreading. The code 104 means: take 10, add 4 zeros = 100,000 pF = 0.1µF = 100nF. To read any 3-digit code correctly, treat the third digit as the number of zeros to append to the first two, not as a third significant digit. Only a two-digit marking with no multiplier would be read as a direct pF value — so “47” = 47 pF, but “470” = 47 pF (four zeros would make it 470,000 pF, but the multiplier here is 0, meaning no zeros added, giving 47pF).

Q2: What does the letter after the capacitor code mean — for example, “104K”?

The letter is the tolerance code. K = ±10%, J = ±5%, M = ±20%, F = ±1%, and so on. The tolerance letter always follows the capacitance code and never modifies the value. So 104K is 0.1µF ±10%, not 104K-something pF. This tolerance table follows the EIA standard and is shared with the resistor tolerance system.

Q3: I see “2A474J” on a capacitor. How do I read this?

This is a full EIA code with a voltage prefix. Break it down: 2A = 100V (from the EIA DC voltage code table). 474 = 47 × 10,000 = 470,000 pF = 0.47µF. J = ±5% tolerance. So this is a 0.47µF, 100V, ±5% ceramic capacitor.

Q4: What’s the difference between C0G and NP0 on a capacitor?

They are the same dielectric specification. C0G is the EIA code under RS-198, and NP0 (Negative-Positive-Zero) is the informal industry name for the same material that has been in use for decades. Both denote a Class I ceramic dielectric with a temperature coefficient of 0 ±30 ppm/°C. If your design calls for one, the other is a valid substitute as long as capacitance, voltage, and case size match.

Q5: How do I identify a capacitor with no markings at all?

First, check your BOM and assembly drawing against the board reference designator — that should be your primary source of truth. If you genuinely don’t know what component was there (repair work on an unknown board, for instance), remove the capacitor from the board and measure it with an LCR meter or a DMM with capacitance function. In-circuit measurements are unreliable because parallel paths affect the reading. Cross-reference the measured capacitance, voltage tolerance (check from context), and package size against supplier databases like DigiKey, Mouser, or the manufacturer’s datasheet library. For 0402 and smaller packages, physically checking the component reel or bag label is the fastest resolution.

Once you’ve internalized the 3-digit EIA system, the rest of the capacitor code landscape falls into place naturally. The tolerance letter, the voltage prefix, the EIA-198 two-character system — they all follow the same underlying logic: compress the maximum amount of information into the minimum number of characters on the smallest possible component body. Understanding that logic is the real key to reading any capacitor code you’ll ever encounter on a real PCB.