The fundamental distinction
A SKU is your store's internal item code. A GTIN is a standardized trade item identifier assigned within the GS1 system. A barcode is a machine-readable symbol that can encode a GTIN or another identifier. The barcode and the SKU can both point to the same catalog item.
The short answer: identifier comparison table
When setting up your inventory catalog or configuring a point-of-sale terminal, keep this foundational reference handy:
| Term | What it is | Who creates it | Where it is used | Can two stores use different values? |
|---|---|---|---|---|
| SKU | Stock Keeping Unit (internal operational code) | The individual retailer or merchant | Internal POS, stock sheets, purchase orders | Yes (completely customizable by each business) |
| GTIN | Global Trade Item Number (umbrella data standard) | Brand owner / manufacturer via GS1 | Global supply chain, wholesale, retail scanning | No (globally unique to that exact product) |
| UPC | Universal Product Code (specifically UPC-A format) | Brand owner / manufacturer via GS1 | Retail checkout, predominantly North America | No (encodes a unique 12-digit GTIN-12) |
| EAN | European Article Number (specifically EAN-13 format) | Brand owner / manufacturer via GS1 | Retail checkout worldwide outside North America | No (encodes a unique 13-digit GTIN-13) |
| Barcode | Machine-readable optical symbol of bars and spaces | Printed by packaging printer or merchant labeler | Physical packaging, shelf tags, shipping cartons | N/A (it is the visual representation of data) |
In short: a SKU is your own stock code; a GTIN identifies a trade item across organizations; and a barcode is the symbol a scanner reads. UPC and EAN are common retail barcode formats that encode GTINs.
What is a SKU?
A SKU (Stock Keeping Unit) is an internal alphanumeric code that you create to organize and identify merchandise in your own business. It is not regulated by any international standards body:
- Merchant-defined structure: You choose the letters and numbers based on what makes sense to your team, such as DRK-CLD-330 for a cold canned drink or BAK-CRST-REG for a plain croissant.
- Short and human-readable: Good SKUs convey category, variant, and size at a glance, allowing stock clerks and kitchen staff to identify items without a barcode scanner.
- Completely functional without barcodes: A small boutique or cafe can track thousands of items using internal SKUs on clipboards or spreadsheets even if no physical barcode labels exist.
- Private to your business: Your competitor down the street can sell the exact same brand of mineral water under a completely different internal SKU.
What is a barcode?
A barcode is not the data itself; it is an optical, machine-readable pattern of dark bars and light spaces that represents numeric or alphanumeric characters to a scanner camera:
Symbology vs value:
The barcode is the symbol (such as UPC-A, EAN-13, or Code 128); the string printed beneath the bars is the human-readable numeric payload.
Hardware decoding:
When a laser reader or phone camera points at the symbol, it measures the relative width of bars and gaps to reconstruct the underlying digits.
Zero intrinsic product information:
A barcode does not contain price, description, or tax rate; it merely supplies the key that your inventory app uses to look up your product record.
What is a GTIN?
GTIN stands for Global Trade Item Number. Managed globally by the non-profit standards organization GS1, GTIN is the overarching data structure used worldwide to uniquely identify trade items:
Encoded in EAN-8 barcodes for very small retail packages (such as chewing gum or cosmetics) where space is limited.
Encoded primarily in UPC-A barcodes, used predominantly throughout the United States and Canada.
Encoded primarily in EAN-13 barcodes, used across Europe, Latin America, Asia, and globally.
Encoded in ITF-14 or GS1-128 symbols on outer wholesale shipping cartons and master cases.
Industry's 2027 target is for retail POS systems to be capable of reading defined GS1 2D barcodes in addition to existing linear barcodes. GS1 US currently offers an individual GS1 US GTIN for a one-time $30 fee, while other GS1 member organizations provide regional fee structures. In addition, every GTIN contains a GS1 company prefix, an item reference assigned by the manufacturer, and a mathematical check digit at the end to verify scanning integrity.
UPC vs EAN: the historical and geographic distinction
Retailers frequently ask whether they need to convert UPC barcodes to EAN or vice versa. In reality, they are two closely related branches of the same GS1 tree:
Can one product have both a SKU and a barcode?
Yes. In fact, running an efficient small retail shop virtually requires using both identifiers in tandem:
Real-world specialty retail example:
Artisan Whole Bean Coffee 1 kg
COF-BRAZIL-1KG
7891234567890 (EAN-13)
The manufacturer prints the 13-digit EAN-13 barcode on the bag for point-of-sale checkout scanning. Internally, your store assigns the SKU 'COF-BRAZIL-1KG' so that your barista, order sheets, and reorder notes clearly describe Brazilian beans in 1 kg bags without typing 13 digits.
Do you need a barcode for every product in your store?
No. Many successful small businesses operate with a mix of barcoded goods and unbarcoded items identified purely by internal SKU or manual lookup:
- Fresh bakery & cafe foods: Croissants, sandwiches, and espresso drinks prepared behind the counter rarely warrant adhesive barcode stickers.
- Bulk produce and unpackaged goods: Loose apples, grains, or bulk spices sold by weight or count are easiest to record by PLU or name.
- Handmade crafts & boutique goods: Locally made ceramics, knitwear, or art pieces where commercial barcode labeling detracts from product presentation.
- Internal shop supplies: Cleaning sanitizers, thermal register paper rolls, and takeout packaging tracked for operational cost control.
What happens when supplier barcodes change?
Independent retailers frequently get tripped up when a trusted supplier updates packaging. Here is how to handle common supplier barcode transitions:
Packaging graphic redesign:
Manufacturers often keep the same GTIN if product weight and ingredients remain identical; verify whether the digits under the bars have actually changed.
Shrinkflation or size modification:
If a cereal box drops from 400g to 360g, GS1 standards mandate a brand-new GTIN. Update your catalog to track the new size under a fresh record.
Switching suppliers for identical items:
If you switch distributors for white sugar, the manufacturer barcode may remain identical while the supplier item code changes on invoices.
Supplier replaces unit with multi-pack:
Never scan a 6-pack barcode under a single-can SKU; ensure multi-packs have their own distinct catalog entry.
Case barcode vs unit barcode: the packaging hierarchy
Small retailers frequently scan an incoming shipping box only to find an unrecogized 14-digit number. Understanding packaging hierarchy prevents receiving errors:
Printed on the individual chocolate bar or soda bottle scanned by the retail consumer at checkout.
A shrink-wrapped sleeve of 6 units sold together or split open to stock convenience shelves.
Corrugated brown shipping box containing 24 individual units; never scan this symbol as an individual piece count on the retail sales floor.
Why Excel sometimes damages barcode numbers
One of the most common data friction points in small retail occurs when exporting or editing inventory spreadsheets in Microsoft Excel. Default numerical handling can alter how barcode strings are displayed or stored:
Dropping leading zeros:
Cause: Excel treats 012345678905 as the pure number 12345678905, automatically stripping the first zero.
Prevention: Format the entire column explicitly as Text (@) before entering or importing numeric identifiers.
Converting to scientific notation:
Cause: Excel may display long numbers with 12 or more digits in scientific notation (such as 7.89123E+12). Scientific notation alone does not mean digits were destroyed, but viewing or re-saving without formatting can cause confusion.
Prevention: Ensure CSV exports enclose barcodes in quotation marks or import data using the Power Query Text data type.
15-digit precision limit:
Cause: Excel numeric precision is limited to 15 significant digits. Numeric identifiers with 16+ digits can lose precision as digits past the 15th position are converted to zeroes.
Prevention: Barcode and SKU identifiers should therefore be stored and imported as Text where exact preservation matters, preventing any precision loss.
Microsoft Support documentation confirms that numerical precision is limited to 15 significant digits; barcode/SKU identifiers should therefore be stored/imported as Text (@) where exact preservation matters.
How Retail Scan & Stock handles identifiers cleanly
Retail Scan & Stock is built to manage product identifiers cleanly without spreadsheet bugs or hardware complexity:
Camera scanning for standard retail barcodes:
Modern smartphone cameras can scan common retail barcodes and are often sufficient for small-store inventory workflows, decoding UPC-A, EAN-13, and Code 128 barcodes cleanly.
Dedicated internal SKU fields:
Maintain internal shop SKUs alongside manufacturer barcodes so your team can search by either code.
Fast manual lookup for unbarcoded stock:
Easily record count quantities for fresh bakery items, produce, or custom goods using rapid keyboard search.
Protected text-format exports:
Exports structured CSV and Excel spreadsheets that preserve leading zeros and prevent scientific notation corruption.
Free tier with up to 1,000 SKUs:
Manage up to 1,000 catalog SKUs, 5 open documents, 30-day history, 1 supplier, and 1 device on the permanent Free plan.
Frequently Asked Questions
Can I make up my own barcode numbers for products I sell?↓
Yes, but only for internal store use. If you sell exclusively in your own shop, you can generate internal barcodes (often using Code 128). Some marketplaces and retail partners require GS1-licensed GTINs or an approved exemption. Check the current requirements of the channel where you plan to sell.
What is the difference between a UPC-A and an EAN-13 barcode?↓
UPC-A is a 12-digit format widely used in the US and Canada; EAN-13 is a 13-digit format used throughout Europe and the rest of the world. Adding a leading zero to a 12-digit UPC creates an equivalent 13-digit GTIN-13.
Why did my spreadsheet turn a 12-digit barcode into scientific notation?↓
Excel may display long numbers in scientific notation. Scientific notation alone does not mean digits were destroyed, as Excel numeric precision is limited to 15 significant digits. However, barcode/SKU identifiers should therefore be stored/imported as Text (@) where exact preservation matters.
Can two different stores use the exact same SKU for different items?↓
Yes. SKUs are internal to each merchant. A bookstore might use SKU 'BOOK-001' while a cafe uses 'BOOK-001' for an employee handbook or coffee table display.
Do I need a barcode to count inventory on my smartphone?↓
No. While scanning barcodes is faster, Retail Scan & Stock allows you to count unbarcoded items by searching your catalog by product name or SKU.
What is a GTIN-14 and how does it differ from a retail unit barcode?↓
GTIN-14 is a 14-digit identifier assigned to master cases and wholesale shipping cartons. It indicates a package containing multiple individual retail units.