When a customer orders the blue version of a shirt in medium, can you tell at a glance which item to pick? If your product records use a mix of supplier codes, product names, and improvised abbreviations, that simple question can slow down fulfillment—and make inventory harder to trust.
A SKU naming system gives every sellable item a consistent internal identifier. The key is to choose a format your team can use, assign it at the right level, and keep the same SKU across the records that describe that item. Here’s how to build a system that works as your ecommerce catalog grows.
What is a SKU, and what should it identify?
A stock keeping unit, or SKU, is a code you create to identify an item in your own business. Unlike a barcode number such as a UPC or EAN, your SKU is an internal identifier: you decide its format and what its characters mean.
Assign one SKU to each distinct item you sell and track separately. If a T-shirt comes in three sizes and two colors, that usually means six variant SKUs. The product name may be shared, but each size-color combination has its own stock count and needs its own identifier.
A useful rule is: if two items cannot be substituted when you pick an order, they should not share a SKU. The same applies when you need to track their inventory separately because they have different packaging, conditions, or other characteristics that matter to your operation.
How to create a SKU naming system step by step
1. Decide which details need to appear in the code
A good ecommerce SKU is recognizable without trying to describe everything about the product. Common components include a product category, a short product identifier, and variant details such as color or size.
For example, a clothing store might use this structure:
CATEGORY-PRODUCT-COLOR-SIZE
Using that format, TEE-104-BLU-M could identify product 104, a blue T-shirt in medium. TEE-104-BLU-L identifies the large version. The difference is easy to spot in a product list or picking sheet.
Only encode details that are stable and useful to your team. A price, promotion, sales channel, or supplier name may change while the physical item stays the same. Those details are generally better kept in separate fields.
2. Write down your formatting rules
Consistency matters more than choosing the perfect abbreviation. Set a few rules before you start assigning SKUs:
- Use one separator: Hyphens make segments readable; use them consistently if your systems allow them.
- Standardize abbreviations: Decide whether blue is BLU, BLUE, or something else, and keep that choice in a shared reference list.
- Keep the order fixed: Don’t put size before color for some products and after it for others.
- Choose a consistent number format: If product identifiers use three digits, write 007 rather than switching between 7, 07, and 007.
- Check system restrictions: Before adopting a format, confirm which characters and lengths your store, inventory software, warehouse tools, and sales channels accept.
Avoid codes that differ only by characters your team might confuse, such as the letter O and the number 0. If staff will read SKUs from labels, keep them reasonably short and legible.
3. Build a small set of examples before committing
Test your proposed format against your actual catalog—not just your simplest product. Try a single-variant item, a product with several options, an item that does not fit your usual category, and any bundle or kit you sell.
| Item | Example SKU | What it distinguishes |
|---|---|---|
| Blue T-shirt, medium | TEE-104-BLU-M | Product, color, and size |
| Blue T-shirt, large | TEE-104-BLU-L | A separate size with its own stock |
| Ceramic mug, white | MUG-207-WHT | A product with no size option |
| Mug and coaster set | SET-031 | A bundle sold as one offering |
Your categories and codes do not need to match these examples. What matters is that a new team member could follow your rules and produce the same SKU you would.
4. Assign a SKU when a sellable item is created
Make SKU assignment part of your product setup process, rather than a cleanup task after items go live. Before publishing a new listing, check that every inventory-tracked variant has a unique SKU and that the code has not been used before.
Maintain a simple SKU reference document that defines your format, approved abbreviations, and the person or team responsible for assigning new codes. If several people add products, this prevents two people from independently creating different codes for the same item—or the same code for different items.
How to keep inventory records organized after assigning SKUs
Creating the code is only the first step. Your SKU must connect the product listing, stock count, purchasing records, and fulfillment workflow to the same item.
Keep one master record for each SKU
Whether you use inventory software or a spreadsheet, give each SKU one master item record. Useful fields may include the product name, variant attributes, barcode if applicable, supplier reference, storage location, stock quantity, and whether the item is active or discontinued.
Keep those details in their own fields instead of squeezing them into the SKU. For example, a storage location can change when you rearrange your warehouse; the item’s identity does not.
Match stock movements to the correct item
Use SKUs on purchase orders, receiving records, picking lists, returns, and stock adjustments wherever your workflow supports them. When incoming stock arrives, check both the SKU and the actual variant before updating the quantity. A correct-looking code on the wrong size of product is still an inventory error.
Review stock regularly to catch mismatches between recorded and physical quantities. If you sell through multiple channels, establish which system holds the authoritative inventory record and how each channel’s listings map to it. Systems may use different listing identifiers; what matters is that every listing points to the correct item and stock count.
Document bundles and multipacks separately
A bundle may need its own sellable SKU even when its contents already have individual SKUs. Record which component SKUs and quantities make up the bundle—for example, one mug and one coaster per set.
Decide how your inventory process will deduct those components when a bundle sells. Do not assume that creating a bundle SKU automatically updates component stock; that depends on your software and setup. The same principle applies to multipacks: a three-pack sold as one offering needs a clear relationship to the units used to assemble it.
Common SKU mistakes to avoid
- Reusing an old SKU: A discontinued item’s code may still appear in past orders and reports. Give a genuinely new item a new code.
- Changing SKUs to reflect a new name or price: If the item itself has not changed, update those fields rather than breaking the connection to its existing records.
- Using one SKU for every variant: You cannot reliably distinguish stock for different sizes or colors if they share an identifier.
- Encoding too much information: Long codes are harder to enter, read, and maintain. Keep changeable information in product fields.
- Using supplier codes as your only internal system: Supplier references are useful, but they may not be unique across your catalog or remain stable when you change suppliers.
How to introduce a new SKU system to an existing store
If you already have products and orders, changing SKUs calls for more care than starting from scratch. First, export your current product and variant records and save a backup. Build a mapping of old SKU → new SKU for every item you plan to change, alongside the product or variant identifier used by your platform.
Check the mapping for duplicates, missing variants, and codes assigned to the wrong items. Then confirm how your store, integrations, shipping tools, and sales channels handle SKU changes before updating live records. Some workflows rely on a SKU as the link between systems, so changing it in only one place can disrupt order or inventory matching.
Test a small group of items first. Verify that listings display correctly, orders identify the right variants, and stock updates flow as expected. Keep the old-to-new mapping for historical lookups rather than assuming past records will update everywhere. If your existing SKUs already work well, you may be better off applying the new rules only to future products.
A simple system is easier to maintain
The best SKU naming system is one your business can use consistently. Start with a short, documented format; give each separately tracked item a unique code; and keep product details and stock movements tied to that code. Before your next product launch, test the format on a few real items and add SKU assignment to your listing checklist. That small habit can make receiving, picking, and inventory reviews much easier to manage.
Frequently asked questions
Do SKUs have to be unique?
Yes, within your inventory system, each separately tracked item should have a unique SKU. Two different variants sharing a code can make stock counts and order fulfillment ambiguous.
Is a SKU the same as a barcode?
No. A SKU is an internal code you assign. A barcode is a machine-readable representation of an identifier, which might be your SKU or a separate number such as a UPC or EAN. Keep both in your product record when you use both.
Should each color and size have its own SKU?
Usually, yes. If you sell or stock each color-size combination separately, assign each combination its own SKU so you can identify what is available and what a customer ordered.
Can I change a SKU after a product has been sold?
You can, but check the impact first. Orders, integrations, sales-channel listings, and reports may refer to the old code. Document the change, update connected systems where needed, and retain a mapping so you can interpret historical records.