The Small Business Adminstration's size standards define whether a business entity is small and, thus, eligible for Government programs and preferences reserved for "small business" concerns. Size standards have been established for types of economic activity, or industry, generally under the North American Industry Classification System (NAICS).
NAICS is described in the North American Industry Classification Manual - United States. The manual includes definitions for each industry. NAICS assigns codes to all economic activity within twenty broad sectors. Section 121.201 provides a full table of small business size standards matched to the U.S. NAICS industry codes. A full table matching a size standard with each NAICS Industry or U.S. Industry code is also published annually by the SBA in the Federal Register.
Read more about Small Business Size Regulations.
Source: Code of Federal Regulations, Title 13, Part 121 - Small Business Size Regulations
