Learn to decode capacitor markings including 3-digit codes, tolerance letters, voltage ratings, polarity symbols, and temperature coefficients — with full reference charts.

Walk into any electronics lab and pick up a random capacitor. Chances are it has a string of numbers, letters, or cryptic codes printed on its body that tell you exactly what it is — if you know how to read them. The problem is most beginners (and plenty of intermediate engineers) have never been properly taught the system. They guess, they Google individual values, or they just trust whatever the BOM says.

Capacitor markings are a complete language once you learn the grammar. In this guide, I’ll break down every type of marking you’ll encounter — value codes, voltage ratings, tolerance letters, polarity indicators, temperature coefficients, and schematic symbols — so you can decode any capacitor you pick up, whether it’s a through-hole electrolytic or a tiny 0402 ceramic SMD.

Why Reading Capacitor Markings Correctly Is Critical on a PCB

A misread capacitor marking can mean the difference between a working circuit and a damaged board. I’ve seen engineers pull a “104” ceramic cap and a “105” ceramic cap from the same tray because the last digit was hard to read under poor lighting. That’s a 10× capacitance difference — more than enough to kill a carefully tuned filter or destabilize a voltage regulator.

Every capacitor placed on a PCB carries specific marking information that must match the schematic, BOM, and component datasheet. Getting comfortable with these markings is a core competency for anyone doing board bring-up, rework, or quality inspection.

Capacitor Schematic Symbols Explained

Before we get to physical markings, it helps to understand how capacitors appear on schematics. Different types of capacitors use different symbols, and misreading a symbol can lead to using the wrong component type entirely.

Standard (Non-Polarized) Capacitor Symbol

The basic capacitor symbol consists of two parallel lines — representing the two conductive plates — separated by a gap. Both lines are straight and identical, indicating there is no polarity. This symbol is used for ceramic, film, mica, and other non-polarized capacitor types.

Polarized Capacitor Symbol

For electrolytic and tantalum capacitors, one plate is shown as a curved line (the negative plate) and the other remains straight. A “+” symbol is sometimes added near the positive terminal. Always check for this curved line before placing an electrolytic in your circuit — it’s telling you that polarity matters.

Variable Capacitor Symbol

A variable capacitor (trimmer or tuning cap) is shown with an arrow drawn diagonally through the standard capacitor symbol, indicating that the capacitance can be adjusted.

Capacitor Symbol Reference Chart

Symbol Type	Appearance Description	Capacitor Type
Two straight parallel lines	Equal parallel plates	Ceramic, film, mica (non-polarized)
One curved line + one straight line	Unequal plates	Electrolytic, tantalum (polarized)
Parallel lines + diagonal arrow	Adjustable symbol	Trimmer, variable capacitor
Parallel lines + “+” marker	Polarity marked	Electrolytic (alternative notation)
Feedthrough symbol	Line through plates	EMI feedthrough capacitor

How to Read Capacitor Markings on Through-Hole Capacitors

Electrolytic Capacitor Markings

Electrolytic capacitors are usually large enough to print the full value directly on the body. A typical marking looks like this:

470µF 35V 105°C

Breaking that down:

Marking Element	Example	Meaning
Capacitance value	470µF	470 microfarads
Voltage rating	35V	Maximum operating voltage
Temperature rating	105°C	Max operating temperature
Polarity stripe	White/light stripe on body	Indicates negative terminal
Longer lead	Positive lead	Anode (+)
Shorter lead	Negative lead	Cathode (−)

The negative stripe runs the full height of the can and is clearly visible. On PCBs, the silkscreen will show a “+” marker for the positive pad. Always cross-reference both.

Film Capacitor Markings

Film capacitors follow a similar convention to ceramics but are large enough to print readable values. You’ll see markings like 0.1µF 250V or 100nF 63V. The voltage rating on film caps tends to be high — they’re often used in mains-connected circuits.

How to Read Capacitor Markings on Ceramic Capacitors

This is where things get technical. Small ceramic capacitors — especially SMD types — have almost no room for printing, so they use compact code systems.

The 3-Digit Capacitance Code (EIA Standard)

The most widely used ceramic capacitor marking system uses a 3-digit number. The result is always expressed in picofarads (pF).

Rule: First two digits = significant figures. Third digit = number of zeros (multiplier).

3-Digit Capacitor Code Chart

Marking Code	Calculation	Value in pF	Converted Value
010	01 × 10⁰	1 pF	1 pF
100	10 × 10⁰	10 pF	10 pF
101	10 × 10¹	100 pF	100 pF
102	10 × 10²	1,000 pF	1 nF
103	10 × 10³	10,000 pF	10 nF / 0.01 µF
104	10 × 10⁴	100,000 pF	100 nF / 0.1 µF
105	10 × 10⁵	1,000,000 pF	1 µF
220	22 × 10⁰	22 pF	22 pF
221	22 × 10¹	220 pF	220 pF
472	47 × 10²	4,700 pF	4.7 nF
683	68 × 10³	68,000 pF	68 nF
334	33 × 10⁴	330,000 pF	330 nF

Special case — the “9” multiplier: When the third digit is 9, it means × 0.1. So “229” = 22 × 0.1 = 2.2 pF.

Tolerance Code Letters on Ceramic Capacitors

After the 3-digit value code, a single letter indicates the tolerance — how close the actual capacitance is to the marked value:

Letter Code	Tolerance	Use Case
A	±0.05 pF	Ultra-precision RF
B	±0.1 pF	Precision RF, oscillators
C	±0.25 pF	RF matching
D	±0.5 pF	High-precision circuits
F	±1%	Precision filters, timing
G	±2%	General precision
J	±5%	Standard signal circuits
K	±10%	General purpose bypass
M	±20%	Power supply decoupling
Z	+80% / −20%	Non-critical bulk use

For an IC decoupling application, K or M is fine. For a crystal oscillator load capacitor or an active filter, you need F or better.

Voltage Rating Codes on Ceramic Capacitors

When space allows, a letter or number-letter code indicates the voltage rating:

Code	Voltage Rating
0G	4 V
0J	6.3 V
1A	10 V
1C	16 V
1E	25 V
1H	50 V
1J	63 V
2A	100 V
2D	200 V
2E	250 V
2H	500 V
3A	1000 V

On many small SMD ceramics (0402, 0201), voltage and tolerance codes are omitted entirely due to space constraints — you have to check the reel label or datasheet.

Temperature Coefficient Codes — The Dielectric Identifier

One of the most important (and most overlooked) capacitor markings is the temperature coefficient code. This tells you what dielectric material is used and how the capacitance will behave across temperature.

EIA Temperature Coefficient Codes for Ceramic Capacitors

Code	Also Known As	Temp Range	Capacitance Change	Best Use
C0G	NP0	−55°C to +125°C	±30 ppm/°C (virtually zero)	RF, oscillators, precision timing
X5R	—	−55°C to +85°C	±15%	General SMD decoupling
X7R	—	−55°C to +125°C	±15%	Wide-temp decoupling, filtering
X8R	—	−55°C to +150°C	±15%	High-temp automotive
Y5V	—	−30°C to +85°C	+22% / −82%	Non-critical bypass only
Z5U	—	+10°C to +85°C	+22% / −56%	Older designs, avoid for new work

This is the marking that trips up engineers most often. A Y5V capacitor can lose over 80% of its rated capacitance at temperature extremes or under DC bias. If your schematic calls for 10µF X7R and you substitute Y5V “because it’s the same value,” the circuit may not work correctly in real conditions.

Decoding the EIA temperature code system:

The code uses a three-part structure. For X7R as an example:

• X = lower temperature limit (−55°C)
• 7 = upper temperature limit (125°C)
• R = maximum capacitance change (±15%)

First Letter	Lower Temp Limit
X	−55°C
Y	−30°C
Z	+10°C

Middle Number	Upper Temp Limit
2	+45°C
4	+65°C
5	+85°C
6	+105°C
7	+125°C
8	+150°C
9	+200°C

Last Letter	Max Capacitance Change
P	±10%
R	±15%
S	±22%
T	+22% / −33%
U	+22% / −56%
V	+22% / −82%

Tantalum Capacitor Markings

Tantalum capacitors are polarized and have their own marking convention. Most through-hole tantalum caps print the value directly (e.g., 4.7µF 16V) with a “+” marking on the positive lead.

SMD tantalum caps (the small rectangular ones with a stripe at one end) follow this convention:

Marking Element	Description
Stripe / band	Indicates the POSITIVE terminal (opposite to electrolytic convention — don’t confuse them)
Value code	Printed value in µF
Voltage code	Letter or number-letter system similar to ceramics

This is a critical difference to remember: on electrolytic caps, the stripe marks the negative terminal. On tantalum SMD caps, the stripe marks the positive terminal. Mixing this up is one of the most common capacitor polarity mistakes in SMD rework.

SMD Capacitor Package Sizes and What They Tell You

SMD capacitors don’t always have visible markings, but the package size itself communicates usable capacitance ranges:

Package Code	Dimensions (mm)	Typical Capacitance Range	Typical Use
0201	0.6 × 0.3	1 pF – 100 nF	High-density RF, mobile
0402	1.0 × 0.5	1 pF – 10 µF	General SMD, decoupling
0603	1.6 × 0.8	1 pF – 22 µF	Standard SMD design
0805	2.0 × 1.25	1 pF – 47 µF	Higher capacitance SMD
1206	3.2 × 1.6	100 pF – 100 µF	High capacitance, power
1210	3.2 × 2.5	1 nF – 100 µF	High voltage / high cap
1812	4.5 × 3.2	1 nF – 100 µF	High voltage safety caps

When a ceramic cap has no printed marking at all — which happens frequently on 0201 and 0402 parts — your only way to identify it is from the reel label, the BOM, or by measuring with an LCR meter.

Complete Capacitor Marking Quick-Reference Chart

Marking Type	Where Found	What to Look For	Decoding Method
3-digit code (e.g., 104)	Ceramic, film caps	Three numbers	First 2 digits + zeros = pF value
Tolerance letter (e.g., K)	Ceramic caps	Single letter after value code	See tolerance table above
Voltage code (e.g., 1H)	Ceramic caps	Letter+number or number+letter	See voltage table above
Temp code (e.g., X7R)	Ceramic caps	3-character code on reel/datasheet	See EIA temp code table
Direct value (e.g., 470µF)	Electrolytic, film	Full value printed on body	Read directly
Polarity stripe	Electrolytic	Stripe = negative terminal	Opposite side is positive
Polarity stripe	Tantalum SMD	Stripe = positive terminal	Stripe side is positive
European notation (e.g., 4n7)	Older components	Letter used as decimal point	4n7 = 4.7 nF

Useful Resources for Decoding Capacitor Markings

Resource	Type	Link
Digi-Key Capacitor Parametric Search	Component Database	digikey.com/capacitors
Murata Product Catalog	Datasheet Library	murata.com
TDK Capacitor Finder	Datasheet Library	product.tdk.com
KEMET Capacitor Selector	Product Database	kemet.com
Vishay Capacitor Documents	Application Notes	vishay.com/capacitors
Mouser Electronics Search	Distributor Database	mouser.com/capacitors
EIA-198 Standard	Industry Standard	eia.org
All About Circuits	Educational Reference	allaboutcircuits.com

Frequently Asked Questions About Capacitor Markings

1. What does “104” mean on a ceramic capacitor?

The code “104” means 10 followed by 4 zeros in picofarads: 100,000 pF, which equals 100 nF or 0.1µF. This is the single most common decoupling capacitor value in digital electronics. You’ll see it on SMD ceramics and through-hole discs alike. The calculation is always: first two digits (10) × 10 to the power of the third digit (10⁴) = 100,000 pF.

2. How do I tell the positive from negative terminal on a capacitor?

On through-hole electrolytic capacitors, the longer lead is positive and the can usually has a stripe marking the negative terminal. On SMD electrolytic caps, look for the “−” marking or stripe on the negative side. On SMD tantalum capacitors, the stripe or band marks the positive terminal — the opposite convention from electrolytics. Non-polarized types like ceramic and film caps have no polarity and can be connected either way.

3. What does X7R mean on a capacitor?

X7R is a temperature coefficient code for ceramic capacitors. It means the capacitor operates from −55°C (X) to +125°C (7) with a maximum capacitance change of ±15% (R) across that range. It’s a general-purpose dielectric — better stability than Y5V/Z5U but not as precise as C0G/NP0. X7R is the most commonly specified dielectric for bypass and decoupling caps in commercial electronics.

4. Why do some SMD capacitors have no markings at all?

Very small SMD capacitors — particularly 0201 and 0402 package sizes — are often left blank because there simply isn’t enough surface area to print readable characters. The component identity is carried on the reel label and in the BOM. If you’ve lost track of a blank SMD capacitor, your only option is to measure it with an LCR meter and cross-reference the value with your design documentation.

5. What does the voltage rating on a capacitor marking mean, and can I use a higher-rated cap?

The voltage rating is the maximum DC voltage the capacitor can safely handle across its terminals. Exceeding it risks dielectric breakdown and component failure. Using a higher-rated capacitor is generally safe and often recommended — a 50V-rated cap in a 12V circuit has more headroom and will typically last longer. Just verify that the physical size fits your footprint and that the capacitance value hasn’t shifted significantly due to the dielectric characteristics of the higher-voltage part.

Final Thoughts on Reading Capacitor Markings

Capacitor markings are a compact but information-dense system once you understand the rules. The 3-digit code gives you the value, the tolerance letter tells you accuracy, the voltage code sets your operating limit, and the temperature coefficient code (especially for ceramics) tells you how the component will behave across the real operating range of your product.

The polarity distinction between electrolytic and tantalum SMD caps is the one that bites engineers most often on rework — so print out that reference table and keep it at your workbench. The few minutes spent learning to decode these markings will save you hours of troubleshooting bad boards.