How many digits are in an official SIC code?
An official detailed SIC Industry uses four digits. Two-digit Major Groups and three-digit Industry Groups are broader levels within the same hierarchy.
Structure of SIC Codes
The official U.S. Standard Industrial Classification is a hierarchy that moves from broad industry divisions to detailed four-digit industries. The levels are Division, two-digit Major Group, three-digit Industry Group, and four-digit Industry.
The 1987 SIC Manual defines 83 two-digit Major Groups, 416 three-digit Industry Groups, and 1,005 four-digit Industries. The official U.S. SIC structure ends at four digits.
Extended SIC classifications add commercial detail below the official four-digit Industry. They are useful for more specific business-data segmentation, but they are not additional official government SIC levels.
Updated: September 2026 · Reviewed by the SICCODE.com Industry Classification Review Team
The four levels of the official SIC hierarchy
Each level narrows the classification. The Division identifies a broad part of the economy, while the four-digit Industry provides the most detailed official SIC classification.
| Level | Format | Purpose | Example |
|---|---|---|---|
| Division | Letter | Broadest SIC grouping of economic activity. | Division I, Services |
| Major Group | 2 digits | Groups related industries within a Division. | 73, Business Services |
| Industry Group | 3 digits | Groups closely related four-digit Industries. | 737, Computer Programming, Data Processing, and Other Computer Related Services |
| Industry | 4 digits | Most detailed official SIC classification. | 7372, Prepackaged Software |
What the digits in a SIC code represent
The digits are hierarchical. In a four-digit SIC code, the first two digits identify the Major Group, the first three digits identify the Industry Group, and all four digits identify the Industry.
- 73
- Major Group 73, Business Services
- 737
- Industry Group 737, Computer Programming, Data Processing, and Other Computer Related Services
- 7372
- Industry 7372, Prepackaged Software
The Division letter is not part of the four-digit numeric code. Major Groups fall within the ranges assigned to each Division.
How many official SIC codes are there?
U.S. Bureau of Labor Statistics documentation for the 1987 SIC Manual reports 83 Major Groups, 416 Industry Groups, and 1,005 detailed four-digit Industries.
| Level | Code format | Number defined in the 1987 SIC Manual |
|---|---|---|
| Major Group | 2 digits | 83 |
| Industry Group | 3 digits | 416 |
| Industry | 4 digits | 1,005 |
These counts refer to the official 1987 SIC structure. Extended SIC classifications are a separate commercial layer and should not be added to the official government totals.
SIC divisions and Major Group ranges
The Division level provides the broadest view of the SIC structure. The 1987 framework uses Divisions A through K, with Division K reserved for establishments that cannot be classified in another Division.
| Division | Major Group range | Title |
|---|---|---|
| A | 01-09 | Agriculture, Forestry, and Fishing |
| B | 10-14 | Mining |
| C | 15-17 | Construction |
| D | 20-39 | Manufacturing |
| E | 40-49 | Transportation, Communications, Electric, Gas, and Sanitary Services |
| F | 50-51 | Wholesale Trade |
| G | 52-59 | Retail Trade |
| H | 60-67 | Finance, Insurance, and Real Estate |
| I | 70-89 | Services |
| J | 91-97 | Public Administration |
| K | 99 | Nonclassifiable Establishments |
Example of a SIC code from Division to Industry
SIC 1731, Electrical Work, shows how the levels connect:
- Division C
- Construction
- Major Group 17
- Construction Special Trade Contractors
- Industry Group 173
- Electrical Work
- Industry 1731
- Electrical Work
A broader analysis can roll the establishment up to Major Group 17 or Division C, while detailed classification uses the four-digit Industry 1731.
How Not Elsewhere Classified categories fit into SIC
SIC includes residual categories titled “Not Elsewhere Classified,” commonly abbreviated NEC. These categories provide a defined classification when an activity belongs within a broader group but does not fit one of the more specifically named Industries.
Many NEC codes end in 9, including 7389 Business Services, Not Elsewhere Classified and 8999 Services, Not Elsewhere Classified. A 9 should not be treated as a universal shortcut for determining classification. The Industry title and definition should be checked before using an NEC code.
An NEC Industry is not a general catch-all for any uncertain business. Use it only when the activity fits the broader SIC group and no more specific Industry definition applies.
Official four-digit SIC and Extended SIC
The official U.S. SIC structure ends at four digits. Commercial business-data systems may add additional detail below the four-digit Industry to support more specific market segmentation and classification.
The Extended SIC classifications shown at SICCODE.com are continually reviewed and updated to reflect changes in the business environment, including emerging industries, new products and services, evolving business models, and activities that are not separately identified in the official 1987 SIC structure.
Extended SIC does not replace the official four-digit Industry. The four-digit SIC remains the classification anchor, while the extended code provides an additional commercial detail layer.
Browse the Extended SIC Code Lookup for the current classifications available on SICCODE.com.
SIC digit levels are not equivalent to NAICS digit levels
SIC and NAICS use different hierarchies. A two-digit SIC Major Group is much more specific than a two-digit NAICS Sector, so the systems should not be compared by digit count alone.
| SIC | NAICS |
|---|---|
| Division, letter level | Sector, 2 digits |
| Major Group, 2 digits | Subsector, 3 digits |
| Industry Group, 3 digits | Industry Group, 4 digits |
| Industry, 4 digits | NAICS Industry, 5 digits; U.S. National Industry, 6 digits |
The extra NAICS hierarchy levels do not mean that NAICS is simply SIC with two additional digits. The systems were developed differently, industry boundaries can differ, and a SIC-to-NAICS crosswalk may produce one or several candidate codes.
See NAICS vs SIC Codes for the broader comparison.
Using the SIC hierarchy for classification and analysis
The appropriate level depends on what is being classified or analyzed.
- Use the four-digit Industry when a detailed official SIC classification is needed.
- Use the three-digit Industry Group to combine closely related four-digit Industries.
- Use the two-digit Major Group for broader industry-family analysis.
- Use the Division level for the broadest SIC rollups.
- Use Extended SIC when more commercial detail is useful, while retaining the official four-digit SIC as the underlying anchor.
When choosing a code for a particular business or establishment, structure alone is not enough. The activity should be compared with the relevant SIC Industry definitions and classification guidance.
Primary sources
The hierarchy, official counts, establishment concept, and Industry descriptions on this page are based on U.S. government SIC references.
-
National Technical Information Service, Standard Industrial Classification Manual, 1987
Government record for the 1987 SIC Manual published by the U.S. Office of Management and Budget. -
U.S. Bureau of Labor Statistics, Quarterly Census of Employment and Wages Field Definitions
Reports the 1987 SIC hierarchy counts of 83 Major Groups, 416 Industry Groups, and 1,005 four-digit Industries and describes the Division structure. -
Occupational Safety and Health Administration, Standard Industrial Classification Manual
Current searchable government presentation of the 1987 SIC hierarchy, Major Groups, Industry Groups, Industries, and descriptions. -
Occupational Safety and Health Administration, SIC System Search
Supports lookup of two-, three-, and four-digit SIC classifications and Industry descriptions.
Questions about SIC code structure
What is the most detailed official SIC level?
The four-digit Industry is the most detailed official level in the 1987 U.S. SIC structure.
How many four-digit SIC Industries are there?
The 1987 SIC Manual defines 1,005 four-digit Industries according to U.S. Bureau of Labor Statistics documentation.
What do the first two digits of a SIC code mean?
The first two digits identify the Major Group. The first three digits identify the Industry Group, and the complete four-digit code identifies the Industry.
Is a six-digit SIC code official?
No. The official U.S. SIC structure ends at four digits. Six-, seven-, and eight-digit Extended SIC classifications are commercial detail layers used by business-data systems.
Does a code ending in 9 always mean Not Elsewhere Classified?
No. Many residual SIC categories use codes ending in 9 and titles containing Not Elsewhere Classified, but the title and Industry definition should always be checked rather than relying on the final digit alone.
Is a two-digit SIC code equivalent to a two-digit NAICS code?
No. Two-digit SIC represents a Major Group, while two-digit NAICS represents a much broader Sector. The hierarchy levels are not equivalent by digit count.