The main difference between SIC and NAICS codes is how the two systems organize industries. NAICS was designed around a production-oriented concept, grouping establishments that use similar processes to produce goods or services. SIC uses its established industry structure and a broader mix of classification principles, with many industries organized around the type of product or service provided.
Their hierarchies are also different. NAICS moves from broad sectors to 6-digit U.S. industries, while SIC moves from broad divisions to 2-digit Major Groups, 3-digit Industry Groups, and 4-digit Industries. Despite the different code lengths, the two systems contain a very similar number of detailed official industries.
NAICS and SIC are different classification systems, not the same system with different code lengths. NAICS uses a production-oriented framework and more hierarchy levels; SIC reaches detailed industry classifications with fewer levels. Because their industry structures differ, NAICS and SIC codes do not always map one-to-one.
Reviewed by the SICCODE.com Industry Classification Review Team · Updated September 2026
The most important differences are the classification concept, hierarchy, and industry boundaries. The number of digits alone does not tell you which system is more useful or how many detailed industries it contains.
| Difference | NAICS | SIC |
|---|---|---|
| How industries are organized | Uses a consistent production-oriented concept, grouping establishments with similar production processes. | Uses the established SIC industry structure and a broader mix of classification principles, including product or service activity. |
| Broad classification level | Begins with broad 2-digit Sectors, such as Manufacturing or Health Care and Social Assistance. | Begins with broad Divisions, then moves to more specific 2-digit Major Groups such as Food and Kindred Products or Health Services. |
| Official hierarchy | 2-digit Sector → 3-digit Subsector → 4-digit Industry Group → 5-digit NAICS Industry → 6-digit U.S. National Industry. | Division → 2-digit Major Group → 3-digit Industry Group → 4-digit Industry. |
| Detailed official industries | 1,012 U.S. industries in 2022 NAICS. | 1,005 official 4-digit industries in the 1987 SIC system. |
| What the code length means | More hierarchical levels before reaching the detailed industry. | Fewer hierarchical levels, but not dramatically fewer detailed industries. |
| Current government use | Current U.S. federal statistical classification standard and widely used across government statistical and administrative programs. | Still used in selected government systems, including SEC EDGAR; OSHA also maintains the searchable 1987 SIC Manual. |
| Business-data use today | Widely used in business databases, analytics, segmentation, research, reporting, and other industry-classification workflows. | Widely used in business databases, customer and prospect classification, segmentation, targeting, financial and insurance applications, analytics, and other commercial workflows. |
| Conversion between systems | Mappings can be one-to-one, one-to-many, or many-to-one. A crosswalk is useful for conversion, but it does not mean the two industry definitions are exact equivalents. | |
NAICS uses a production-oriented concept. Establishments are grouped into the same industry when they use similar processes to produce goods or services. Its hierarchy uses more levels between the broad sector and the detailed U.S. industry.
The classification looks at the establishment's production activity and operating process rather than merely the final product name, customer type, or marketing description.
See the NAICS Classification & Reference Center for detailed assignment, boundary, and verification guidance.
SIC groups establishments through its established industry structure, using a broader mix of classification principles than NAICS. Product or service activity is an important part of many SIC classifications, while other parts of the system reflect production or market-oriented factors.
SIC provides recognizable industry groupings at relatively early levels of its hierarchy. Its 2-digit Major Groups are substantially more specific than NAICS 2-digit Sectors, and its 4-digit industries provide the detailed official classification level.
See the SIC Classification & Reference Center for detailed SIC classification and non-governmental Extended SIC guidance.
NAICS is not simply SIC with two additional digits. It uses a different classification concept and hierarchy, so industry boundaries do not line up perfectly. As a result, some SIC industries split into several NAICS industries, several SIC industries can correspond to one NAICS area, and some activities are grouped differently between the two systems.
The classification methods are different, but both NAICS and SIC are used today. NAICS is the current U.S. federal statistical classification standard. That does not mean all federal agencies stopped using SIC. SIC remains in use in selected government systems as well as business databases, financial and insurance applications, segmentation, analytics, targeting, and other commercial workflows.
SIC also remains in active use in selected U.S. government systems. For example, the SEC continues to assign SIC codes to companies in EDGAR and uses SIC classifications in its Division of Corporation Finance to help assign filing-review responsibility. OSHA also continues to maintain the searchable 1987 SIC Manual as a government reference.
In business datasets, NAICS and SIC can both be maintained as industry-classification fields. Different end users may rely on NAICS, SIC, or both depending on their software, methodology, analytics, segmentation, targeting, reporting, or other business requirements.
NAICS can support company classification, segmentation, market analysis, benchmarking, CRM enrichment, and industry filtering using the current NAICS hierarchy.
SIC can support company classification, customer and prospect segmentation, targeting, financial and insurance analysis, commercial database organization, and workflows built around SIC industry groupings.
NAICS-to-SIC and SIC-to-NAICS crosswalks are useful for finding likely corresponding industries, but they are not always exact conversions. Because the systems classify and organize industries differently, a mapped code should not automatically be treated as an identical industry definition.
The systems' official histories explain why they coexist in modern data environments.
NAICS was adopted in 1997 as the new federal standard for classifying business establishments for statistical purposes. It is developed cooperatively by the United States, Canada, and Mexico and is reviewed periodically.
SIC preceded NAICS as the U.S. federal statistical industry-classification system. The 1987 SIC Manual remains the principal official SIC reference. NAICS is the current federal statistical standard, but that does not mean all federal agencies stopped using SIC. SIC remains in active use in selected U.S. government systems. For example, the SEC continues to assign SIC codes to companies in EDGAR and uses SIC classifications in its Division of Corporation Finance to help assign filing-review responsibility. OSHA also continues to maintain the searchable 1987 SIC Manual as a government reference. SIC is also widely used in business databases, financial and insurance applications, segmentation, analytics, targeting, and other commercial workflows.
These government references document the structural and conceptual differences between the systems.
NAICS consistently groups establishments by similarities in how goods or services are produced. SIC uses its established industry structure and a broader mix of classification principles, including the type of product or service activity.
The official U.S. NAICS hierarchy extends to 6-digit national industries, while official U.S. SIC ends at the 4-digit industry level. The number of digits alone does not make the systems directly comparable because their industry structures also differ.
Not by very much at the most detailed official level. 2022 NAICS contains 1,012 U.S. industries, while the 1987 SIC system contains 1,005 official 4-digit industries. NAICS uses more hierarchical levels, but the two systems have a very similar number of terminal industry categories.
Yes. SIC remains in use in selected current U.S. government systems, including SEC EDGAR classifications, and OSHA continues to maintain the searchable 1987 SIC Manual. SIC is also widely used in business data, customer and prospect classification, segmentation, financial and insurance applications, analytics, targeting, vendor systems, and historical datasets.
Yes. A business can be classified under both systems. Which classification is used depends on the requirements of the database, software platform, analysis, reporting process, targeting workflow, or other application.
Not always. Because the systems use different structures and classification concepts, mappings may be one-to-one, one-to-many, or many-to-one.
NAICS replaced SIC as the U.S. federal statistical standard. That change did not mean all federal agencies stopped using SIC, and it did not eliminate SIC from business databases, commercial applications, historical datasets, or selected current government systems such as SEC EDGAR.