# SMD Resistor Code Identification Guide
## Introduction to SMD Resistors
Surface Mount Device (SMD) resistors are widely used in modern electronics due to their compact size and excellent performance. Unlike through-hole resistors, SMD resistors don’t have color bands but instead use numerical codes to indicate their resistance values. Understanding these codes is essential for anyone working with electronic circuits.
## Standard SMD Resistor Code Systems
There are three main coding systems used for SMD resistors:
### 1. Three-Digit Code System
This is the simplest system, typically used for resistors with 5% tolerance. The first two digits represent significant figures, and the third digit represents the multiplier (number of zeros to add).
Example: “472” means 47 × 10² = 4700 ohms or 4.7kΩ
### 2. Four-Digit Code System
Used for more precise resistors (1% tolerance), this system works similarly but with three significant digits and one multiplier digit.
Example: “4701” means 470 × 10¹ = 4700 ohms or 4.7kΩ
### 3. EIA-96 Code System
This advanced system uses two numbers and one letter for high-precision resistors. The numbers represent a code from a lookup table, and the letter indicates the multiplier.
Example: “01A” means 100 × 10⁰ = 100 ohms
## How to Read SMD Resistor Codes
Follow these steps to decode SMD resistor markings:
- Identify the code system (3-digit, 4-digit, or EIA-96)
- For 3-digit codes: First two digits = significant figures, third digit = multiplier
- For 4-digit codes: First three digits = significant figures, fourth digit = multiplier
- For EIA-96 codes: First two digits = value code (refer to table), letter = multiplier
- Multiply the significant figures by the multiplier to get the resistance value
Keyword: SMD Resistor Code
## Common SMD Resistor Packages
SMD resistors come in various standard sizes:
| Package Code | Dimensions (mm) | Power Rating |
|---|---|---|
| 0201 | 0.6 × 0.3 | 1/20W |
| 0402 | 1.0 × 0.5 | 1/16W |
| 0603 | 1.6 × 0.8 | 1/10W |
| 0805 | 2.0 × 1.25 | 1/8W |
| 1206 | 3.2 × 1.6 | 1/4W |
## Special Cases and Exceptions
Some SMD resistors may have additional markings or exceptions:
- Resistors with values below 10 ohms may use ‘R’ to indicate the decimal point (e.g., “4R7” = 4.7 ohms)
- Some manufacturers use additional letters to indicate tolerance (
