How SIC Code Digits Work: 2, 3, 4, 6, 7, and 8-Digit SIC Code Structure
Summary: Standard Industrial Classification (SIC) Codes use a hierarchical, digit-based structure to categorize business activities. Official SIC codes are defined at the 4-digit level, while 6-, 7-, and 8-digit versions are commonly used as extended, non-standard subdivisions for added analytical or marketing granularity.
Standard Industrial Classification (SIC) Codes are a hierarchical system used to categorize industries based on a business’s primary economic activity. The structure progresses from broad groupings to more specific industry definitions as additional digits are added.
At the highest level, the first two digits identify a major industry group. For example, SIC codes ranging from 20–39 represent the Manufacturing sector. Within this range, SIC Code 20 designates Food and Kindred Product Manufacturing, serving as a broad umbrella for multiple food-related industries.
Breaking Down SIC Code Digits
As SIC codes progress from two to four digits, the classification becomes more specific and standardized. Official U.S. SIC definitions stop at the four-digit level, which is the recognized reference point for historical reporting, regulatory alignment, and longitudinal analysis.
Within SIC Code 20, four-digit codes differentiate between distinct food manufacturing activities such as meat processing, dairy production, grain milling, and bakery products. This structure enables analysts, researchers, and businesses to compare industries consistently across datasets and time periods.
Business Targeting and Extended SIC Codes
In commercial databases and B2B marketing tools, SIC codes are often extended beyond four digits to six, seven, or eight digits. These extended SIC codes are not part of the official government standard but are vendor-defined subdivisions built on top of four-digit SIC industries.
It is important to note that an eight-digit SIC code is not inherently “more accurate” than a six-digit code. Instead, the additional digits represent alternative levels of detail defined by the data provider. The structure and meaning of these extensions can vary between databases.
Example of SIC Code Progression
The table below illustrates how SIC codes become more specific as digits are added, and where extended SIC codes typically appear in commercial classification systems.
| Digits | Code | Description | Classification Type | Link |
|---|---|---|---|---|
| 2-digit | 20 | Food and Kindred Product Manufacturing (Major Industry Group) | Official SIC grouping | View SIC 20 |
| 3-digit | 201 | Meat Products (Industry Group) | Official SIC grouping | View SIC 201 |
| 4-digit | 2011 | Meat Packing Plants | Official SIC (standardized) | View SIC 2011 |
| 6-digit | 201103 | Sausage Makers | Extended SIC (vendor-defined) | View Extended 201103 |
Applications of Extended SIC Codes
Extended SIC codes are commonly used for market segmentation, competitive analysis, and internal business intelligence. By subdividing official four-digit SIC industries, organizations can identify narrower segments within a broader market.
These extensions are particularly useful in marketing and analytics workflows where precision targeting is required. However, because extended SIC structures are not standardized, they should be documented carefully when used in reporting or shared analysis.
Leveraging SIC Codes for Business Analysis
Businesses can use four-digit SIC codes as a standardized anchor and apply extended SIC codes for finer internal classification. This approach balances consistency with flexibility, allowing organizations to maintain comparability while still gaining detailed market insights.
SIC-based classification also supports clearer communication with partners, analysts, and stakeholders by providing a shared industry framework, especially when paired with transparent documentation of any extended coding used.
The Role of SIC Codes Today
Although the SIC system has been largely superseded by NAICS for federal statistical reporting, SIC codes remain widely used in legacy datasets, historical analysis, and commercial applications. Extended SIC codes continue to evolve within private classification systems to meet modern analytical and marketing needs.
Organizations that understand the distinction between official SIC codes and extended SIC classifications are better positioned to apply industry data accurately and defensibly across research, strategy, and operational use cases.