What are NAICS codes?
The North American Industry Classification System (NAICS) is the standard used by the United States, Canada, and Mexico to classify business establishments by their primary economic activity. In government contracting, NAICS codes serve as the bridge between what agencies buy and which businesses can compete.
Every federal contract opportunity is assigned a NAICS code. This code determines the small business size standard — the threshold below which a firm qualifies as "small" for that particular contract. NAICS codes are also used for market research, economic analysis, and small business goal tracking.
How are NAICS codes structured?
NAICS codes follow a hierarchical structure from broad to specific:
2-digit codes represent sectors (e.g., 54 — Professional, Scientific & Technical Services). 3-digit codes represent subsectors (e.g., 541 — Professional, Scientific & Technical Services). 4-digit codes represent industry groups (e.g., 5415 — Computer Systems Design and Related Services). 5-digit codes represent industries (e.g., 54151 — Computer Systems Design and Related Services). 6-digit codes represent national industries (e.g., 541512 — Computer Systems Design Services).
Federal contracts are typically assigned 6-digit NAICS codes, though some solicitations use less specific codes. The 2-digit sector level is useful for market overview analysis — identifying which broad industries receive the most federal contracting dollars.
How do NAICS codes affect government contracting?
NAICS codes impact government contracting in three critical ways:
First, size standards. The SBA assigns a size standard to each NAICS code. For example, NAICS 541512 (Computer Systems Design) has a $34 million revenue size standard, while NAICS 236220 (Commercial Building Construction) has a $45 million standard. A firm could be "small" under one code and "large" under another.
Second, opportunity discovery. Contractors filter SAM.gov opportunities by NAICS code to find relevant work. If you select the wrong codes during SAM.gov registration, you may miss opportunities or appear in searches for work you can't perform.
Third, set-aside eligibility. Some set-aside programs (like WOSB) only apply to specific NAICS codes designated by the SBA. Your NAICS code determines which set-aside programs you can access.
How do you find the right NAICS codes for your business?
Start by searching the NAICS code database at census.gov/naics. Enter keywords that describe your primary business activity and review the code descriptions. You can also look at competitors' SAM.gov registrations to see which codes they use.
Most businesses register multiple NAICS codes — a primary code that best represents their core activity, plus secondary codes for additional capabilities. There's no penalty for registering multiple codes, but you should only claim codes where you can genuinely perform the work.
For each contract you bid on, the contracting officer assigns a NAICS code. You must be below the size standard for that specific code to bid as a small business, regardless of which codes you have in your SAM.gov profile.
What are the most common NAICS codes in federal contracting?
The most heavily used NAICS codes in federal contracting reflect the government's major spending categories. In IT and professional services: 541512 (Computer Systems Design), 541511 (Custom Computer Programming), 541519 (Other Computer Related Services), 541330 (Engineering Services), and 541611 (Administrative Management Consulting).
In facilities and support services: 561210 (Facilities Support Services), 561720 (Janitorial Services), 561612 (Security Guards and Patrol Services), and 238220 (Plumbing and HVAC Contractors).
In defense and manufacturing: 336411 (Aircraft Manufacturing), 334511 (Search and Navigation Equipment), and 336413 (Other Aircraft Parts Manufacturing).
You can explore award data by NAICS sector on our industry analytics pages to see which codes receive the most federal contract dollars.