SKU (stock keeping unit)

A SKU is a short code that identifies one exact sellable item: a specific product, in a specific size, color and pack. "HOOD-BLU-M" is a SKU. "Hoodie" is not, because it covers twelve different things you can put in a box. The code is yours: you invent it, and it only has to make sense inside your business.

It concerns anyone who holds stock or sends orders to someone who does. A creator with 15 products can get by with names for a while. The first time a warehouse, a supplier or a spreadsheet is involved, names stop working and codes take over.

What is a SKU?

A SKU (stock keeping unit) is an internal identifier assigned by the seller to each distinct item they stock and sell. Every combination that needs its own quantity gets its own SKU. A t-shirt in 4 sizes and 3 colors has 12 SKUs, and a 3-pack of the black one in size L is a 13th.

It is not a barcode. A barcode (EAN in Europe, UPC in North America) is a number assigned by a global registry so that any retailer can scan the same product. A SKU is private and free. The same product can have one EAN and different SKUs in two stores. Many small sellers never need a barcode and always need SKUs.

It is not a product ID either. A product ID is a number your store software assigns automatically, usually meaningless. A SKU is readable by a human and carries information.

Vocabulary around it: "parent product" (the hoodie), "variant" (blue, size M), "SKU count" (how many distinct items you manage), and "SKU rationalization" (removing the ones that do not sell).

Why it matters

Everything operational happens at the SKU level. Inventory is counted per SKU. Orders list SKUs. Returns are checked against SKUs. Supplier purchase orders are written in SKUs. Reports on margin, velocity and dead stock are only useful per SKU.

A worked example. A brand sells a tote bag in natural and black. Without SKUs, the stock says "tote: 60". Black sells three times faster. In week 4 the store still shows 22 totes available, but all 22 are natural, and eleven customers order black. Eleven refunds, eleven apologies, and the reorder is placed two weeks late because nobody saw black hit zero. With two SKUs, TOTE-NAT and TOTE-BLK, the black one shows sold out at the right moment and the reorder goes out on time.

The cost side matters too. When you know that HOOD-BLU-M sells 40 a month and HOOD-YEL-XS sells 2, you stop reordering yellow XS and free the cash. Without SKUs, you reorder "hoodies" in the same mix every time.

How it works

Building a SKU system for a small store, step by step:

• List the attributes that change stock. Usually product, color, size, and sometimes material or pack size. Ignore attributes that do not create a separate unit (a gift message is not a SKU).
• Pick a fixed order. Product code first, then attributes in the same order every time: product, color, size. Never size before color on one product and the reverse on another.
• Choose short codes for each value. BLU, BLK, NAT for colors. XS, S, M, L, XL for sizes. Two to four characters per segment.
• Separate segments with a dash. HOOD-BLU-M reads instantly. HOODBLUM does not.
• Avoid letters that look like digits. No O and 0, no I and 1 in the same system.
• Create one SKU per variant before you sell it. Adding SKUs after orders exist means editing history.
• Never reuse a SKU. A retired code stays retired. Reusing it corrupts every past report.
• Put the SKU on the physical item. A label on the shelf, bag or box, so whoever packs the order picks the right one.

A single product with no variants still gets a SKU. "CNDL-LAV-200" for a 200 g lavender candle is one code, and the 500 g version is a different one.

Benchmarks and examples

• SKU length. 6 to 14 characters. Shorter than 6 runs out of room; longer than 14 gets typed wrong.
• SKU count for a creator. 10 to 80 SKUs is typical. A store with 20 designs of prints in 3 sizes already has 60.
• SKU count for a small brand. 100 to 1,000. Beyond that, a spreadsheet stops being enough and you want the store to hold the master list.
• Share of dead SKUs. In most catalogs, 20% to 30% of SKUs produce under 5% of revenue. Review them twice a year.
• A creator example. A ceramicist sells mugs in 3 glazes and 2 sizes. Her scheme is MUG-[glaze]-[size]: MUG-WHT-S, MUG-WHT-L, MUG-GRN-S and so on. Six SKUs, each with its own count and its own shelf label.
• A brand example. A streetwear brand uses [product family][year]-[color]-[size]: TEE24-BLK-M. The year segment lets them retire a season without confusing it with next year's version of the same tee.
• A digital example. A creator selling three course tiers uses CRS-BASIC, CRS-PRO, CRS-TEAM. No stock, but the codes make reports and refunds unambiguous.

Common mistakes

• Using the supplier's SKU as your own. Change supplier and every code changes with it. Keep your own scheme and map the supplier's code to it.
• Encoding the price in the SKU. Prices change, codes should not. HOOD-BLU-M-49 is broken the day the hoodie costs $55.
• One SKU for a product with variants. The stock number becomes meaningless the moment one variant sells faster.
• Codes that only one person understands. X7Q-22B tells the person packing on Saturday nothing. HOOD-BLU-M tells them everything.
• Changing a SKU after it has been sold. Old orders, returns and reports now point at a code that no longer exists.

Best practices

• Write the scheme down on one page. Product prefixes, color codes, size codes, segment order. Anyone who joins can create a correct SKU in a minute.
• Make it human-readable first, machine-friendly second. The person picking the item at 6 pm needs to read it without a lookup table.
• Keep a master list. One sheet or one catalog with every SKU, its product, variant, cost and supplier reference. The store's catalog is the best place for it.
• Add the SKU to every packing slip and label. It removes wrong-item shipments, which are among the most expensive returns.
• Retire, do not delete. Mark a SKU as discontinued and keep it in the list. History depends on it.
• Review SKU velocity twice a year. Sort by units sold in 6 months. Stop reordering the bottom 20% unless they serve a purpose.
• Match bundles to their own SKU. A 3-pack is a separate SKU with its own price, and your process must decrement the three component SKUs when it sells.

In Roctify

Every product and every variant in Roctify carries its own SKU field, stored once in the shared catalog and used by every channel. The same SKU shows on orders whether the customer bought from your link-in-bio page or your online store, and stock is tracked against it, so a sale of HOOD-BLU-M on any channel decrements the same quantity everywhere.

SKUs appear in orders and in the exports and reports available on the Pro plan, which lets you pull sales per SKU into a spreadsheet and see which variants move and which do not. Digital products, courses and downloads can carry a SKU too, which keeps refunds and reports unambiguous even when there is no stock to count.

FAQ

Do I need a SKU if I only sell a few products?

Yes, and it is easiest to set up when you have few products. Five products with no variants means five codes, done in ten minutes. The value shows up the first time you add a second color, hire someone to pack, or export a sales report. Adding SKUs after two years of orders is far more work than adding them on day one.

Can two products share the same SKU?

No. The whole point of a SKU is that it points to exactly one item. If two things can share a code, you cannot know which one sold, which one is in stock, or which one came back. Bundles, gift sets and sample sizes each get their own SKU.

What is the difference between a SKU and an EAN or UPC barcode?

A SKU is your private code, invented by you, free, and only meaningful inside your business. An EAN or UPC is a global number purchased from a registry so that any retailer's scanner recognizes the product. You need an EAN to sell in physical retail or on large marketplaces. You need SKUs for everything, from the first day.