How to create SKU numbers: a simple system, examples and the mistakes to avoid

Short answer: You create SKU numbers yourself, for free: a SKU (stock keeping unit) is an internal code that only your business uses. Pick the few attributes that tell your products apart (for example category, model, color and size), give each attribute a short fixed code, and join them in the same order every time, such as TSH-CLS-BLK-M for a classic black T-shirt in medium. Each product and each variant gets its own SKU, and no two items ever share one. Keep codes short, avoid spaces and symbols, and use letters that cannot be confused with numbers. A SKU is not a UPC: barcodes for retail and marketplaces come from GS1, while SKUs are yours. If you sell the same product on several marketplaces, use the same SKU everywhere, so a dashboard that matches the same product across marketplaces by its SKU can keep stock in step.

What a SKU number is, and what it is not

Shopify's help center defines SKUs as codes "you can use internally to track your inventory and report on your sales." Three things follow from that:

• You create it. No one issues SKUs and there is nothing to buy.
• It is internal. It means something inside your business; another store may use a different SKU for the very same product.
• It identifies one stockable item. A red shirt in small and a red shirt in large are two SKUs, because you count and pick them separately.

SKU vs UPC. GS1 US puts the difference in one line: a UPC "is accepted globally for that product, while a SKU number is internal and created by a specific brand or retailer." The UPC is the number behind the barcode, in North America usually the 12-digit format, and GS1 US says every variation, "like a different size or flavor", gets its own number. On its price table (read on 26 October 2026), a single GS1 US GTIN costs $30 with no annual renewal, and a company prefix for 10 items costs $250 plus $50 a year. You can sell with SKUs alone in your own store, but marketplaces and retailers usually ask for a barcode as well, so plan for both and keep a column for each.

How to create SKU numbers, step by step

1. List what makes your products different. Write down the attributes a picker or a customer would use to tell two items apart: product type, brand or collection, model, color, size, material, pack size. Most stores need three or four.

2. Choose the order. Go from general to specific: category first, variant details last. Then never change the order. Shopify advises that "each letter and number needs to have a purpose" and that you use the same abbreviations across all products.

3. Give every attribute a short code. Build a small lookup table and keep it in a shared sheet:

• Category — Value: T-shirt; Code: TSH
• Model — Value: Classic; Code: CLS
• Color — Value: Black; Code: BLK
• Size — Value: Medium; Code: M

4. Join the parts with a separator. Shopify notes that dashes and underscores help separate attributes. TSH-CLS-BLK-M reads at a glance; TSHCLSBLKM does not.

5. Check the result against the rules below before you print a single label.

6. Record it everywhere. Put the SKU into your store, your marketplace listings, your spreadsheet and your shelf labels, and use exactly the same string in each place.

The rules that keep a SKU system working

Shopify's guidance (read on 26 October 2026) is a good checklist for any channel:

• Unique per variant. "Each product and variant must have its own unique SKU." Shopify warns that duplicates "can cause issues with third-party integrations and inventory tracking."
• Short. Shopify suggests no more than 16 characters, and says 4 to 8 can be enough for a small catalog.
• No spaces, symbols or special characters, which cause search problems.
• No look-alikes. Avoid formats where 0 and 1 can be mistaken for O and I.
• Room to grow. Design the system so new products, colors and sizes fit without renaming the old ones.
• Do not start with a zero. Spreadsheets often strip leading zeros, so 0042 quietly becomes 42. (Our own advice, not Shopify's.)
• Do not build in things that change, such as price, supplier or the year, unless you are sure they never will.

SKU number examples

Shopify gives two formats that show both styles:

• Numeric, apparel: `####-###-###`, for example 4225-776-3234: brand 4225, leg style 776 (boot cut), size 32x34.
• Alphanumeric, pens: `###_###_##`, for example WAL_BLK_25: walnut body, black ink, 2.5 mm point.

Two more, as assumptions for illustration:

• Clothing: HOOD-ZIP-NVY-XL for a navy zip hoodie in XL. Size and color go last, because they change most often within one design. This is the usual answer to "how to create SKU numbers for clothing": one SKU per color and size combination.
• Home goods: MUG-12OZ-WHT-4PK for a pack of four white 12 oz mugs. Pack size belongs in the SKU, because a single mug and a four-pack are counted separately.

How to create SKU numbers in Excel

If your attribute codes sit in columns B to E, one formula builds the SKU in column F:

`=UPPER(B2&"-"&C2&"-"&D2&"-"&E2)`

Copy it down the sheet, then check for duplicates with conditional formatting (Home > Conditional Formatting > Highlight Cells Rules > Duplicate Values). Format the SKU column as text so leading characters are kept. Once a SKU is in use, copy the values and paste them as values, so editing the attribute columns later does not silently change live SKUs.

SKUs on Shopify, Amazon and other marketplaces

• Shopify: you add the SKU in the Inventory section of the product or variant and save. Shopify requires SKUs to be unique within your admin.
• Amazon: each listing has its own SKU field for your code, separate from Amazon's product number and the barcode. We could not read Amazon's Seller Central rules on SKU length and characters, so check the listing template before you upload; a scheme that stays short and uses only letters, numbers and dashes is the safest starting point.
• Other marketplaces: each one has its own SKU field ("stock code" on Turkey's Trendyol, for example). The important part is the same everywhere: one product, one SKU, typed identically on every channel.

Using one SKU across several marketplaces

A SKU system pays off most when you sell in more than one place. If a product is "TSH-CLS-BLK-M" in your store but "tshirt black m" on a marketplace, no tool and no colleague can tell they are the same item, and stock gets counted twice. Three habits help:

• Keep one master list of SKUs, with the barcode next to each.
• Create the SKU before the listing, never the other way round.
• Never reuse a SKU for a different product, even after the old one is discontinued.

The same discipline makes onboarding easier on a new marketplace; we cover the listing step in our guide on how to sell on onbuy, and the fees that come after it in our guide to the trendyol commission rate.

How Pratienda helps

Pratienda is a multichannel dashboard for Trendyol, Hepsiburada and N11, the leading marketplaces in Turkey. It does not connect to Shopify, Amazon or Square. On those three marketplaces, Pratienda recognizes the same product by its stock code (SKU) and merges it into one product card, which is why a clean SKU system matters from day one. When an item sells on one marketplace, stock drops on the others too, and every order lands in one list with its status. If you have your own GS1 company prefix, it also generates EAN-13 barcodes automatically. Starter is $59 a month (tax excluded).

See Pratienda →

FAQ

Do I have to buy SKU numbers?
No. SKUs are internal codes you create yourself at no cost. What you may have to buy is a barcode number: GS1 US lists a single GTIN at $30 and a 10-item company prefix at $250 plus $50 a year.

Can two products share a SKU?
No. Every product and every variant needs its own SKU; Shopify warns that duplicates cause problems with integrations and inventory tracking. If two items are counted separately on your shelf, they need two SKUs.

Is a SKU the same as a UPC or barcode?
No. A UPC is a globally recognized product number issued through GS1 and printed as a barcode. A SKU is your own code, and you can print it as a barcode on your shelf labels too. Keep both, side by side, in your product list.

Sources: Shopify Help Center, "Using SKUs to manage your inventory"; GS1 US, "What is a UPC Code?". Information as of 26 October 2026; prices and platform rules may change.