A code conversion or crosswalk shows how categories in one classification system relate to categories in another. It can help connect SIC, NAICS, and ISIC records across datasets, but a mapped result is not automatically an equivalent industry.
Classification systems differ in structure, definitions, industry boundaries, editions, and the units they are designed to classify. A conversion can therefore be one-to-one, one-to-many, or many-to-one. When more than one candidate is possible, the underlying activity and definitions must be reviewed before a final code is selected.
Updated: September 2026 · Reviewed by the SICCODE.com Industry Classification Review Team
A crosswalk, also called a concordance, records relationships between categories in different classification systems or different editions of the same system. The relationship can be direct, partial, split across several categories, or dependent on the activity being classified.
Official crosswalk tables are useful for understanding structural relationships. The U.S. Census Bureau publishes NAICS concordances that include relationships among several NAICS editions, between 1987 SIC and 1997 NAICS, between 1987 SIC and 2002 NAICS, and between selected NAICS editions and ISIC.
| Mapping type | What it means | How to interpret it |
|---|---|---|
| One-to-one | One source category corresponds closely to one target category. | Usually the simplest case, but definitions and editions should still be verified before treating the codes as equivalent. |
| One-to-many | One source category is divided among two or more target categories. | The correct target depends on the specific activity represented by the record. |
| Many-to-one | Several source categories are combined into one broader target category. | The conversion can reduce detail. Preserve the source code when historical or analytical detail matters. |
| Partial relationship | Only part of one source category corresponds to the target category. | Do not assign the target based on the code number or title alone. Review the activity and boundary language. |
The examples below show a close SIC-to-NAICS correspondence and a one-to-many mapping using live conversion results.
These examples use the live SICCODE.com SIC to NAICS conversion results. They show how to read a mapped result. They are not a substitute for reading the target definition.
A slaughtering plant that processes cattle, hogs, or similar livestock is stored in a source file as 1987 SIC 2011, Meat Packing Plants. The conversion returns one leading NAICS candidate.
| Field | Value |
|---|---|
| Source record | A meat-packing establishment whose primary activity is slaughtering livestock. |
| Source classification | SIC 2011, Meat Packing Plants |
| Candidate classification | NAICS 311611, Animal (except Poultry) Slaughtering |
| How to use the result | This is a close correspondence. Verify the current NAICS definition, inclusions, exclusions, and edition before treating 311611 as the final classification. |
Open the live mapping: Convert SIC 2011 to NAICS.
A food-service establishment is stored as 1987 SIC 5812, Eating Places. That SIC industry covers a wide range of eating places. NAICS separates many of those activities, so the conversion returns several candidate NAICS industries. The source code cannot identify which one applies.
| If the establishment's activity is | Leading candidate among the returned NAICS codes |
|---|---|
| Preparing meals and serving seated customers | 722511 Full-Service Restaurants |
| Preparing food that customers order at a counter or similar limited-service format | 722513 Limited-Service Restaurants |
| Operating a cafeteria, grill buffet, or buffet | 722514 Cafeterias, Grill Buffets, and Buffets |
| Selling snacks or nonalcoholic beverages for immediate consumption | 722515 Snack and Nonalcoholic Beverage Bars |
| Preparing food under contract for another organization's facilities | 722310 Food Service Contractors |
| Preparing food for events at the customer's location or another event site | 722320 Caterers |
| Producing live theatrical performances and serving food as a dinner theater | 711110 Theater Companies and Dinner Theaters |
If the record is a neighborhood restaurant with table service, 722511 is the leading candidate among those results. If customers order at a counter and take the food themselves, 722513 is the leading candidate. Do not assign the first returned code by default. Compare the actual activity with each target definition. Open the live mapping: Convert SIC 5812 to NAICS.
These classification systems were developed for different statistical, administrative, and analytical contexts. They do not share identical hierarchies or industry boundaries. SIC continues to be widely used in business data and selected government, financial, analytical, and regulatory systems. NAICS is the U.S. federal statistical standard.
Digit count should not be used as a shortcut for conversion quality. A six-digit NAICS code is not automatically a more detailed version of a four-digit SIC code, and NAICS is not SIC with two additional digits.
Use the lookup below to open the matching conversion tool. Enter a 4-digit SIC code, a 6-digit NAICS or ISIC code, or a keyword. The results page lists candidate mappings. If more than one code is returned, review the activity and target definitions before selecting a final classification.
| Tool | Use it when | How to interpret the result |
|---|---|---|
| SIC to NAICS Conversion | A record contains an SIC classification and a NAICS relationship is needed. | Treat returned NAICS codes as candidate classifications. If several appear, identify which target definition matches the actual activity. |
| NAICS to SIC Conversion | A record contains a NAICS classification and an SIC relationship is needed. | Review the official four-digit SIC industry definitions. Do not assume one NAICS industry has one exact SIC equivalent. |
| NAICS to ISIC Conversion | North American industry data needs to be related to the UN international industry framework. | Check which NAICS and ISIC editions the relationship represents. Older official concordances may not reflect the latest edition of both systems. |
| ISIC to NAICS Conversion | International industry data needs to be related to a North American industry structure. | Use the candidate relationship as a starting point and verify the current NAICS definition and national context. |
Multiple results usually mean the source category covers activities that the target system separates. The correct target cannot be determined from the source code alone.
Use the business activity, products or services, location function, and other source evidence rather than the company name alone.
Determine whether the source record represents an establishment, enterprise, business location, company, contract, or another unit.
Compare the target categories using their full descriptions, inclusions, exclusions, neighboring classifications, and cross-references.
If the target system requires a primary-activity determination, use that system's methodology rather than choosing the closest keyword match.
Keep the source code, source system, source edition, selected target code, target system, target edition, and any interpretation needed to resolve the mapping.
A crosswalk can narrow the possible target codes, but it cannot always determine which activity is primary for a particular establishment or company record.
For official U.S. NAICS statistical classification, the framework is establishment-oriented and production-oriented. The ideal primary-activity measures are the relative production costs and capital investment associated with the outputs produced. Revenue, shipments, receipts, or employment can be practical proxies when direct measures are unavailable.
Other government, financial, contracting, and commercial systems can maintain company-level SIC or NAICS fields for their own purposes. A conversion does not resolve a mismatch between company-level and establishment-level records by itself.
Classification systems change over time. A conversion is more precise when both the source edition and target edition are known.
The U.S. Census Bureau's public concordance archive includes direct 1987 SIC relationships to 1997 and 2002 NAICS, as well as multiple NAICS edition and ISIC concordances. It should not be interpreted as a single direct official 1987 SIC-to-2022 NAICS table. Do not treat an older concordance as if it maps directly to the latest edition of both systems.
Historical normalization often requires a mapped field so records from different periods can be analyzed together. The safest approach is to preserve the original classification rather than overwriting it.
| Field | Why preserve it |
|---|---|
| Original code | Preserves what the source actually reported or stored. |
| Original system and edition | Provides the context needed to interpret the source code correctly. |
| Mapped code | Supports analysis in the target classification. |
| Target system and edition | Prevents the mapped result from being treated as edition-neutral. |
| Mapping method or source | Shows whether the relationship came from an official concordance, internal mapping rule, or definition-level review. |
| Ambiguity or review flag | Identifies records where one source classification had multiple plausible targets. |
| Situation | Recommended treatment |
|---|---|
| One source code maps to one target and the definitions align closely | Use the relationship as the leading candidate, then verify the target definition and edition. |
| One source code maps to several targets | Review the actual activity and candidate definitions before selecting a target. |
| Several source codes collapse into one target | The mapped result may be suitable for broad analysis, but retain the original codes if source detail matters. |
| Source and target editions are unknown | Resolve the version context before treating the conversion as reliable. |
| Company-level source is being converted into an establishment-oriented statistical classification | Confirm what the source field represents and whether location-level activity is available. |
| Regulatory, contracting, underwriting, or filing decision depends on the result | Use the receiving program's rules and definitions. A general crosswalk should not substitute for the program's classification procedure. |
| Mistake | Why it creates problems | Better approach |
|---|---|---|
| Calling every mapped code an equivalent | Many relationships are partial, split, or aggregated. | Use terms such as candidate, related classification, or mapped relationship unless equivalence has been verified. |
| Choosing the first result in a one-to-many mapping | The source code alone does not identify which target activity applies. | Compare the record's activity with each target definition. |
| Using keyword similarity instead of definitions | Similar titles can hide different inclusions, exclusions, and boundaries. | Use full definitions and cross-references. |
| Ignoring source and target editions | Industry definitions can change over time. | Store and verify both editions. |
| Overwriting the original classification | The original source context and detail can be lost. | Keep original and mapped classifications in separate fields. |
| Assuming SIC to NAICS is a simple digit expansion | The systems have different hierarchies and industry boundaries. | Treat the conversion as a cross-system relationship, not a numeric transformation. |
Official concordances and classification manuals are the starting point for understanding structural relationships. Current code selection should still be verified against the applicable target definition.
A crosswalk or concordance records relationships between categories in different classification systems or different editions. It can identify candidate mappings, but it does not guarantee that the categories have identical scope.
The source SIC industry can cover activities that NAICS separates into several industries. The correct NAICS classification depends on which activity the record actually represents.
No. NAICS and SIC have different structures and industry boundaries. A NAICS classification can relate to one SIC industry, several SIC industries, or only part of an SIC industry.
No. NAICS is a different classification framework. The extra digits primarily reflect a different hierarchy and should not be interpreted as a direct extension of SIC.
Yes. Industry definitions and boundaries change between revisions. The source and target editions should be known when the conversion will be used for historical comparison, reporting, or data normalization.
Not when multiple candidate mappings are returned. Compare the actual activity with the target definitions before selecting the final classification.
Usually not when traceability or historical analysis matters. Keep the original classification and store the mapped classification separately with the relevant system and edition.
No. A crosswalk shows relationships between categories. When several target categories are possible, determining primary activity requires evidence about the business or establishment and the methodology of the target system.