The short answer on SIC vs NAICS: use NAICS for anything touching government data, size standards, or modern targeting; keep SIC for SEC filings, insurance workflows, and older vendor files. The systems differ in age (SIC froze in 1987, NAICS refreshes every five years), depth (4 digits vs 6), and coverage. And for building business lists, the winning move is boring: carry both codes on every record.
I’m going to be honest: I ignored SIC codes for years. I figured a standard frozen in 1987 could stay in 1987. Then one client call in 2024 fixed that attitude in about ten minutes, and I’ll tell you that story below.
First, the two systems side by side:
| SIC | NAICS | |
|---|---|---|
| Introduced | The 1930s | 1997 |
| Last updated | 1987 (frozen since) | 2022 (next revision: 2027) |
| Structure | 4 digits, 10 lettered divisions | 6 digits, 20 sectors, hierarchical |
| Code count | About 1,004 four-digit codes | 1,012 six-digit industries (2022) |
| Maintained by | No one (retired standard) | OMB and Census, jointly with Canada and Mexico |
| Where you meet it | SEC EDGAR, insurers, older vendor lists | Census data, IRS, SBA size standards, SAM.gov |
| Best for | Legacy matching and filings | Current targeting and government data |
What SIC Codes Are (and Why They Refuse to Die)
SIC codes are four-digit industry codes from the Standard Industrial Classification, a federal system born in the 1930s and last updated in 1987. Ten lettered divisions (A through J) split the economy into big buckets like Manufacturing, Retail Trade, and Services, and each four-digit code names an industry inside them. Dentists, for example, are SIC 8021, “Offices and Clinics of Dentists”.
Now think about what “frozen in 1987” means. No e-commerce. No software publishing as we know it. No app anything. The modern internet economy gets squeezed into catch-all codes ending in “NEC” (not elsewhere classified), which is exactly as messy as it sounds.
So why does SIC still matter? Because big institutions never migrated. The SEC still assigns SIC codes to every filing company. Insurance underwriting still classifies risk by SIC. Credit bureaus and older data products still index by it. The full code list still lives in the OSHA SIC manual, and it gets read every day. A retired standard, working overtime.
What NAICS Codes Are (and How the Hierarchy Works)
NAICS codes are six-digit industry codes from the North American Industry Classification System, the current federal standard. Here’s the official origin, straight from the Census Bureau:
“NAICS was developed under the auspices of the Office of Management and Budget (OMB), and adopted in 1997 to replace the Standard Industrial Classification (SIC) system.”
U.S. Census Bureau, census.gov/naics
The clever part is the hierarchy. Each digit you add narrows the definition. Walk one code down with me:
- 72 = Accommodation and Food Services (sector)
- 722 = Food Services and Drinking Places (subsector)
- 7225 = Restaurants and Other Eating Places (industry group)
- 722511 = Full-Service Restaurants (the six-digit industry)
So you can target broad or surgical with the same system, just by choosing how many digits to use. NAICS 2022 defines 1,012 six-digit industries across 20 sectors, and the system was built jointly with Canada and Mexico, so codes compare across North America.
🔍 Did You Know? NAICS revises on years ending in 2 and 7. The 2022 vintage is current, and 2027 is next. SIC has not been revised since 1987, which means the gap between the two systems grows with every cycle.
The Differences That Actually Matter for a List
History is nice. But the SIC vs NAICS choice only matters where it changes your list. Five differences do:
- Granularity: six digits split what four digits lump, which decides how precise your market segmentation can get
- Freshness: NAICS tracks the modern economy; SIC pretends 1987 never ended
- Hierarchy: NAICS digits mean something as you add them; SIC codes are flatter
- Comparability: NAICS works across the US, Canada, and Mexico
- Availability: plenty of tools, filings, and vendor files still speak only SIC
And granularity deserves a real example, so here’s one from our own database. SIC 5812, “Eating Places”, holds 1,079,384 US records. One bucket. NAICS splits that same restaurant world into full-service restaurants (722511: 650,371 records), limited-service restaurants (722513: 304,555), and snack and beverage bars (722515: 104,214), plus smaller cousins. Same businesses, different resolution. As of September 2026, those are live counts.
If your offer only fits sit-down restaurants, that split IS your campaign. SIC can’t see it. NAICS can.
When SIC Still Wins
SIC wins whenever the system you’re feeding speaks SIC. Four common cases: SEC and EDGAR workflows, insurance and credit processes, matching a legacy customer file coded years ago, and older government archives you want to trend against.
Here’s my 2024 story. An insurtech client asked for an insurance lead generation target list, and I delivered a beautiful NAICS-coded file. Then their underwriting partner replied that their whole risk model keys on SIC. Just SIC. I spent two days crosswalking six-digit precision into four-digit buckets, watching definitions blur at every step. The lesson wasn’t “NAICS is wrong”. The lesson was that the receiving system decides, and I hadn’t asked.
Since that week, every export I build carries both codes. Two columns. Zero drama. And the data side cooperates: effectively every US record in our database ships with both a SIC and a NAICS value already filled in (18.4 million of 18.4 million in a September 2026 query), so keeping both truly costs nothing.
When NAICS Wins
NAICS wins for almost everything current. The big cases: any Census data (County Business Patterns counts are NAICS-keyed), SBA size standards and loan programs, federal contracting on SAM.gov, modern data vendors, and any campaign that needs six-digit precision.
I found the contracting one by accident. In 2022 I helped a facilities company register on SAM.gov, and the registration asked for NAICS codes, not SIC, to match them with federal opportunities. The government buys by NAICS. If public-sector work is anywhere on your roadmap, your codes are already chosen for you.
And for sizing markets, NAICS is the only real option, because the free count data speaks it natively via County Business Patterns.
What US Businesses Look Like Under Each System
Now the part nobody else publishes. We classified our US local business records under both systems, so you can see how each one carves the same economy. First, NAICS sectors, from 17,246,848 US records carrying an official-list NAICS code as of September 2026:
| NAICS sector | US records | Share |
|---|---|---|
| Health Care and Social Assistance | 2,515,289 | 14.6% |
| Other Services (except Public Administration) | 2,458,515 | 14.3% |
| Retail Trade | 2,457,850 | 14.3% |
| Accommodation and Food Services | 1,445,358 | 8.4% |
| Professional, Scientific, and Technical Services | 1,042,540 | 6.0% |
| Construction | 1,011,752 | 5.9% |
| Arts, Entertainment, and Recreation | 1,010,065 | 5.9% |
| Real Estate and Rental and Leasing | 812,788 | 4.7% |
And the same country under SIC divisions, from 18,149,619 US records with an official-list SIC code:
| SIC division | US records | Share |
|---|---|---|
| Services | 8,700,333 | 47.9% |
| Retail Trade | 3,948,883 | 21.8% |
| Finance, Insurance, and Real Estate | 1,308,291 | 7.2% |
| Transportation and Public Utilities | 1,069,225 | 5.9% |
| Construction | 1,032,948 | 5.7% |
| Manufacturing | 758,016 | 4.2% |
The SIC lumping problem: nearly half of US records land in one division
Source: CUFinder Local Business Database, 210M+ records, September 2026.
Source: CUFinder local business database, September 2026. Shares approximate.
See the story in the numbers? Under SIC, “Services” swallows nearly half the country, because the 1987 scheme lumps health care, food service, repair shops, and salons together. NAICS spreads those same records across distinct sectors you can actually target. Same records, different maps, and honestly the clearest picture of the difference between SIC and NAICS I know how to give you. Two honest notes: a places database indexes every mapped establishment, so community places like churches and parks appear alongside storefronts, and these are database records rather than official establishment counts. For the official census of employers, my breakdown of how many small businesses are in the US reconciles the sources, and the full local business statistics report goes wider still.
Drop to the six-digit level and NAICS shows you one more thing SIC divisions never can: how reachable each slice actually is. Here are the biggest individual NAICS codes in our US records, with contact coverage attached:
| NAICS code | US records | Has website | Has email |
|---|---|---|---|
| 621111 Offices of Physicians | 725,731 | 50.7% | 30.1% |
| 722511 Full-Service Restaurants | 650,371 | 60.3% | 30.0% |
| 813110 Religious Organizations | 563,499 | 47.4% | 29.2% |
| 812112 Beauty Salons | 307,259 | 48.5% | 16.8% |
| 221310 Water Supply & Irrigation Systems | 306,664 | 4.0% | 2.9% |
| 722513 Limited-Service Restaurants | 304,555 | 78.9% | 25.4% |
| 531210 Offices of Real Estate Agents & Brokers | 297,697 | 72.8% | 43.0% |
| 611110 Elementary & Secondary Schools | 264,744 | 58.1% | 48.1% |
The biggest NAICS codes in the US by business records
Source: CUFinder Local Business Database, 210M+ records, September 2026.
Source: CUFinder local business database, US records, September 2026. Shares are approximate.
Two lessons hide in that table. First, contactability swings wildly between codes of similar size: real estate brokers (43.0% with email) are emailable at nearly triple the rate of beauty salons (16.8%), a difference a SIC division view averages away. Second, the 221310 row is a built-in data literacy test. A third of a million “water supply” records with 4.0% website coverage aren’t storefronts; they’re wells, utility districts, and irrigation systems that happen to be mapped. When a code’s fill rates collapse like that, the code is telling you what kind of establishment it really contains before you waste a single credit on it.
Converting Between SIC and NAICS (Crosswalk Guidance)
To convert between the systems, use the official Census concordance tables, and expect one-to-many mappings. The Census Bureau publishes concordances linking every 1987 SIC code to its NAICS successors.
Here’s what those tables reveal, and it explains most conversion pain. The 1987 manual holds about 1,004 four-digit codes, and 453 of them map to MORE than one NAICS code. The champion is SIC 7389, “Business Services, NEC”, which fans out into 42 different NAICS codes. So “just convert it” is often really “make 42 decisions”.
The process that keeps it sane:
- Look up your code in the Census concordance table
- Review every candidate code it maps to, not just the first
- Pick by the written definition, since titles alone mislead
- Keep both codes as columns in your list from then on
📌 Example: Dentists convert cleanly: SIC 8021 maps to NAICS 621210, one to one. Restaurants don't: SIC 5812 fans into half a dozen NAICS codes, from full-service restaurants to caterers. Always check which kind of mapping you're holding before you trust a converted list.
So Which Should You Use for a Business List?
By now you can probably answer the SIC vs NAICS question yourself, but here it is as a cheat sheet. Match the code system to the job:
→ SEC or insurance workflow: SIC → Government data or contracting: NAICS → Prospecting list: filter by BOTH where your tool allows → Evaluating a data vendor: ask which NAICS vintage they use, and whether SIC ships on every record
That last question filters vendors fast, because many tools support neither system. If you want to see it working, you can filter local businesses by SIC or NAICS code in CUFinder, where records carry both systems and 689 official SIC codes and 797 official NAICS codes are in live use across the database. One honest caveat: codes assigned at database scale are automated, and edge cases get misfiled, so sample your code before you build on it. My guide to build a business list by industry turns all of this into a step-by-step workflow, and if geography is your other axis, the list of businesses by ZIP code guide shows how codes and postal filters stack. For general picking-a-tool advice, start with choosing a local business database.
💡 Pro Tip: Whatever you buy or build, require BOTH codes on every record. Storage costs nothing. Re-coding a 40,000-row list after a vendor surprise costs your week.
FAQ: SIC vs NAICS
Should I use SIC or NAICS?
Use NAICS unless the system receiving your list requires SIC. NAICS is current, more precise, and matches all government data. SIC remains necessary for SEC filings, insurance workflows, and legacy files. For prospecting lists, the practical answer is both: filter in NAICS, store both codes.
How do I convert SIC codes to NAICS codes?
Use the official Census Bureau concordance tables, which map every 1987 SIC code to its NAICS counterparts. Expect one-to-many results: 453 of the roughly 1,004 SIC codes map to multiple NAICS codes. Review each candidate’s written definition and pick the ones matching your actual target.
How do I find my SIC or NAICS code?
Search your business activity on the Census NAICS page or NAICS.com, then pick the best-matching definition. For SIC, check the OSHA SIC manual, or your SEC filings if you’re a public company. Business databases also display both codes per record.
What SIC code is my business?
Your SIC code is whichever four-digit code best describes your primary activity, and you may legitimately have several. Agencies and data providers assign them independently, so your bank, your insurer, and a database may hold different codes for you. Pick one primary code and use it consistently.
How many SIC and NAICS codes are there?
About 1,004 four-digit SIC codes exist in the 1987 manual, and NAICS 2022 defines 1,012 six-digit industries. In live business data the spread is narrower: as of September 2026, 689 official SIC codes and 797 official NAICS codes carry records in our database.
Do businesses have both a SIC and a NAICS code?
Usually, yes. Codes are assigned by whoever needs them (the SEC, insurers, statistical agencies, data providers), so most established businesses carry at least one of each. They’re descriptions, not licenses: nothing stops a business from updating its code when its activity changes.
When was NAICS last updated?
NAICS 2022 is the current vintage, and the next revision lands in 2027, following the five-year cadence. The 2022 update restructured retail codes substantially, which is why files coded under NAICS 2017 disagree with 2022-coded files about the same stores. Always note the vintage.
It’s Time to Pick Your Codes
Here’s your five-minute assignment. Take your top target industry and write down three things: its NAICS code, its SIC code, and which one your next campaign’s tools actually speak.
→ NAICS for the targeting → SIC for the legacy systems → both columns on every export, forever
That habit is the entire lesson my 2024 crosswalk detour taught me, and it costs nothing to adopt today. The SIC vs NAICS debate stops being a debate the moment you keep both.
You’ve got this. Which system does your stack run on, SIC, NAICS, or a glorious mix? Tell me in the comments. Especially the mixes. I collect those stories.
References
Bad
Okay
Good
Amazing
