SIC, NACE and NAICS Codes Explained: UK, EU and US Industry Classifications

Every country or trading bloc needs a standard way to group businesses by the type of activity they carry out. Without a shared framework, comparing data across industries - or across borders - is impossible. That is why governments and statistical agencies maintain industry classification systems: agreed lists of codes that assign each economic activity a unique identifier. The problem is that the UK, the European Union, and North America all developed their own systems independently, and they do not map to each other cleanly. If you work across borders, handle data from more than one country, or need to convert a SIC code to a NAICS or NACE equivalent, understanding the difference between these systems is essential.

This article explains what each system is, how they relate to each other, and the practical options for converting between them.

What Is a SIC Code?

In the UK, companies are classified using the Standard Industrial Classification (SIC) system. The current version - SIC 2007 - is maintained by the Office for National Statistics (ONS) and has been the standard since January 2008. Every UK company registered at Companies House must declare at least one SIC code when it incorporates, and can declare up to four. These codes determine how the company is categorised on the public register and in official statistics.

UK SIC 2007 codes are five digits long. The structure is hierarchical:

• Section - a single letter (e.g. Section J = Information and Communication).
• Division - two digits (e.g. 62 = Computer programming, consultancy and related activities).
• Group - three digits (e.g. 62.0 = Computer programming, consultancy and related activities).
• Class - four digits (e.g. 62.01 = Computer programming activities).
• Subclass - five digits (e.g. 62012 = Business and domestic software development). This is the UK-specific level, used only within SIC 2007.

For a full breakdown of SIC sections and what they cover, see our guide to SIC code sections overview.

What Is NACE?

NACE stands for Nomenclature statistique des Activites economiques dans la Communaute Europeenne - the statistical classification of economic activities in the European Community. It is the EU's equivalent of SIC and is maintained by Eurostat, the statistical office of the European Union. The current version is NACE Rev. 2, adopted in 2008.

NACE is used across all EU member states and forms the basis for comparable economic statistics throughout Europe. NACE codes are written with a dot separator at the class level (e.g. 62.01), which distinguishes their format from UK SIC subclasses. Where a SIC code goes to five digits, NACE stops at four digits (the class level), with no fifth-digit subclasses.

For a detailed side-by-side comparison of how SIC 2007 and NACE Rev. 2 map to each other, see our article on SIC to NACE conversion.

What Is NAICS?

NAICS - the North American Industry Classification System - is used in the United States, Canada, and Mexico. It was developed jointly by the three governments and came into effect in 1997, replacing the older Standard Industrial Classification system that had been used in the US since the 1930s. NAICS codes are six digits long, structured hierarchically from two-digit sectors down to six-digit national industries.

NAICS is maintained and updated every five years by the relevant statistical agencies: the US Census Bureau, Statistics Canada, and Mexico's INEGI. The most recent revision at the time of writing is NAICS 2022. If you work with US, Canadian, or Mexican company data - for example, when researching North American markets or matching UK suppliers to US buyers - you will encounter NAICS codes frequently.

How They Relate - the Key Facts

The relationship between the three systems is often misunderstood. Here is what matters:

System	Region	Digit length	Based on
SIC 2007	United Kingdom	5 digits (subclass level)	NACE Rev. 2 (identical to 4-digit class level, with UK-specific 5-digit subclasses)
NACE Rev. 2	European Union	4 digits (class level)	UN ISIC Rev. 4 (with EU-specific additions)
NAICS 2022	USA, Canada, Mexico	6 digits (national industry level)	Developed independently; derived from the old US SIC but restructured; loosely linked to ISIC
CNAE	Brazil	7 characters	ISIC Rev. 4 (adapted for the Brazilian economy)

The critical relationships to understand are:

• UK SIC 2007 is built directly on NACE Rev. 2. At the four-digit class level, they are identical. For example, NACE class 62.01 and SIC class 6201 cover exactly the same activity. The UK simply added a fifth digit to split some classes into more specific UK subclasses. This means converting a UK SIC code to its NACE equivalent is usually straightforward - see our SIC to NACE conversion guide for the detail.
• NACE and NAICS both connect loosely to the UN's ISIC framework, but are structured very differently. The UN's International Standard Industrial Classification (ISIC) is the global reference, and both NACE Rev. 2 and NAICS claim some alignment with ISIC Rev. 4. However, NAICS was designed around the North American industrial structure and uses a different hierarchy and different boundaries for many sectors. There is no clean one-to-one mapping between UK SIC (or NACE) and NAICS for most codes.
• CNAE (Brazil) is also ISIC-derived but adapted for the Brazilian economy. Like NACE, it shares structural similarities with ISIC, but again there is no official direct crosswalk to UK SIC or to NAICS.

How to Convert Between Them

The conversion path depends on which systems you need to move between.

SIC to NACE (or NACE to SIC)

Because UK SIC 2007 is built on NACE Rev. 2, this is the most reliable conversion. At the four-digit level the codes are identical (with minor formatting differences - NACE uses a dot, SIC does not). For example, SIC subclass 62012 maps to NACE class 62.01. For a worked example and an illustrative mapping table covering common sectors, see our dedicated guide on SIC to NACE conversion.

SIC to NAICS (or NAICS to SIC)

There is no official complete SIC-to-NAICS crosswalk published by any UK or US authority. The structural differences between the systems mean that some UK SIC codes map to multiple NAICS codes, some NAICS codes span multiple SIC classes, and some activities are classified differently enough that a direct match is impossible. In practice, a reasonable approximate mapping can be constructed for many common codes, but it should always be treated as indicative rather than definitive.

Our SIC to NAICS converter tool provides approximate NAICS equivalents for UK SIC codes - useful for cross-border research or when matching UK company data with North American classification systems. You can also use our SIC code lookup tool to find or verify a UK SIC code before converting it.

NACE to NAICS

Because UK SIC and NACE are equivalent at the four-digit level, converting NACE to NAICS follows the same approximate approach as SIC to NAICS - there is no clean one-to-one map, and any conversion is indicative.

For any regulatory or compliance-critical purpose - filing with a government body, applying for a licence, or submitting data to a statistical authority - always use the official classification published by the relevant body rather than a crosswalk tool. For the UK, the authoritative SIC 2007 list is published by the ONS. For NACE, consult Eurostat RAMON. For NAICS, consult the US Census Bureau.

Further Resources

If you need to look up, convert, or understand UK SIC codes, our free tools make this straightforward:

• SIC to NAICS converter - get approximate NAICS equivalents for any UK SIC code.
• SIC code lookup - find the right SIC code for any business activity.
• SIC code sections overview - a guide to how the 21 SIC sections are structured.
• SIC to NACE conversion - a detailed guide to converting between UK SIC and EU NACE codes.