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SIC and NAICS Codes

Standard Industrial Classification (SIC) codes are four-digit codes used to identify an industry.

The North American Industry Classification System (NAICS) is gradually replacing the SIC system. The NAICS system uses six-digit codes to identify an industry. The first five digits are standardized in the United States, Canada, and Mexico.

Many sources provide industry information based on these codes. Also, most directories that index companies by industry use SIC and/or NAICS codes.

Most resources that utilize these codes provide their own index to the codes. There are also detailed guides specific to SIC or NAICS codes as well as correspondence tables (see below). If you are unable to determine the appropriate SIC code for an industry but know a company that is part of that industry, look up a company in a database such as Business & Company Resource Center to see what codes are assigned to that company.

NOTE: The codes are standardized to the four or six digit level. Some sources will add additional digits to further specify an industry. The numbers read like decimals, additional digits making the numbers longer, indicating a more specialized industry. These additional digits may or may not be uniform in different sources.

NOTE: The codes themselves are an accepted standard, but the assigning of codes to companies is not centralized or standardized. Each source will assign codes based upon how the publisher/producer interprets what the company does and upon which industries of a large conglomerate are considered the most important. Thus different sources often list varying codes for a particular company.

Sources for Determining SIC and NAICS Codes

Publicly available websites provide information on SIC and NAICS codes:

Many of the research databases* provide SIC and NAICS codes:

Correspondence/Conversion Tables:

Correspondence Tables (free online) from the U.S. Census Bureau.


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