SKU (Stock Keeping Unit): Definition, Functions, and How to Create One

Stock counts are often inaccurate because product codes are inconsistent, not because the team was careless. Two products both listed as “Plain Black T-Shirt” but in different sizes, for example, can easily lead to the wrong item being picked. This article covers what an SKU does, how it differs from a barcode, and numbering rules you can apply right away.

An SKU (stock-keeping unit) is a unique alphanumeric code created by a business to identify every sellable, storable product variant, from brand and category through to color and size. Unlike a barcode, which applies globally, an SKU is internal and designed entirely by the company that uses it, so two retailers may use different codes for the same item.

What Does an SKU Do for a Business?

The main function of an SKU is to serve as the link between processes, not merely a label on a shelf. The same code is used by the warehouse team when picking items, by the cashier at the point of sale, and by the analyst reading the sales report. As long as the code stays consistent, all three processes refer to exactly the same item.

• SKUs make similar variants easy to tell apart. Every size, such as a black T-shirt in M and L, has its own code, so staff never have to guess from the product name.
• Stock counts are based on codes rather than product names, which makes the results more accurate and consistent. This is the foundation of effective warehouse management .
• SKUs make sales analysis easier, letting you identify which variants sell well and which have turned into dead stock (non-moving goods).
• SKUs enable cross-channel synchronization, with a single code used across marketplace catalogs, physical stores, and the warehouse.

SKU, Barcode, and GTIN: What Is the Difference?

The difference comes down to who issues them. You create your own SKU; a GTIN (Global Trade Item Number) is assigned by the brand owner from a number range licensed through GS1 and applies worldwide; a barcode is simply how a machine reads that number without typing errors. The three are often treated as interchangeable, even though their roles differ.

According to GS1 US, the global authority for unique product identification, two retailers can sell the same item under an identical UPC (Universal Product Code) while each keeps its own SKU number.

How to Create an SKU: Code Anatomy and Numbering Rules

An effective SKU code runs from general to specific, with brand and category at the front and variant details at the end. Set this structure early, because changing the scheme after thousands of products are already registered means renumbering labels, catalogs, and sales history. Consistent rules matter far more than creativity when building codes.

As an illustration, the fictional brand Nordika uses the code NRD-PT-BLK-M for a plain black T-shirt in size M.

The scheme expands automatically. One T-shirt model in three colors (BLK, WHT, NVY) and four sizes (S, M, L, XL) produces 12 SKUs, from NRD-PT-BLK-S through NRD-PT-NVY-XL, all sharing the NRD-PT- prefix so they sort together.

Six rules keep an SKU scheme consistent:

• Build the code from general to specific. Put brand and category at the front and variants at the back, so codes sharing a prefix stay grouped.
• Keep the code a reasonable length, usually 8–12 characters. There is no official standard; this range simply reflects common practice.
• Avoid starting a code with a zero, since many spreadsheets and import tools strip leading zeros automatically.
• Avoid characters that look alike, such as the digit 0 and the letter O, or the digit 1 and the letter I, to reduce typing errors.
• Use capital letters and hyphens only. Avoid spaces and special characters, as they can break data imports.
• Never build supplier or manufacturer numbers into an SKU, because those numbers can change and do not belong to your company.

An SKU should not carry details such as price, stock quantity, or supplier name. Once that data changes, the code is obsolete. Overly descriptive codes also slow down daily data entry.

SKUs Inside a System: When Spreadsheets Start to Struggle

At a scale of thousands of variants, manual numbering usually breaks down not because the rules are wrong, but because nothing enforces them. A scheme typically starts to unravel once more than one person adds products without following the same rules, opening the door to duplicates and input errors.

Retail ERP handles this through tiered product master data. In SAP S/4HANA Retail, a parent product (generic article) generates color and size variants automatically, and according to SAP documentation, variant numbers are formed by default from the parent article number plus a three-digit sequential suffix. It is the variant that represents the physical item across every business process. The scheme is enforced by the system rather than by human memory.

FAQ (Frequently Asked Questions)

What is the difference between an SKU and a barcode?

An SKU is an internal code for managing stock. A barcode is a machine-readable visual representation; the number it encodes, the GTIN, is issued through GS1 and applies worldwide. According to GS1 US, two retailers can use the same UPC with different SKU numbers.

How many characters should an SKU have?

There is no official standard; every company sets its own format. Common practice ranges from 8 to 12 characters, enough to hold brand, category, and variant without making manual entry a chore. Only three requirements are non-negotiable: unique, consistently formatted, and never starting with a zero.

Does an SKU need to be registered like a barcode?

No. An SKU is entirely internal and does not need to be registered with any body. What GS1 issues is the GTIN, the global number behind a barcode, in four structures of 8, 12, 13, or 14 digits. Many retail channels and marketplaces require a GTIN for product listings.

Conclusion

Discrepancies in stock count results usually trace back to disorganized product codes rather than a careless team. An SKU scheme that is consistent and enforced from day one prevents most of these problems, and a system maintains that consistency once the number of variants outgrows a spreadsheet. As an SAP Platinum Partner through United VARs, with experience since 1998, Soltius delivers implementation and ongoing support for SAP-based retail solutions , including product master data setup.

For a consultation on SKU structure and product master data in SAP S/4HANA Retail, visit soltius.co.id.