SKU Generator

What is a SKU, exactly?

A Stock Keeping Unit is the smallest unit of a product that your business tracks separately in stock. If you sell a hoodie in three sizes and two colours, that's six SKUs, not one — each combination needs its own code because each is ordered, stocked and sold independently. The SKU is entirely internal: unlike a barcode, no external body issues it or checks it for uniqueness. You're free to build whatever format suits your operation, as long as it stays consistent and unique across your own catalogue.

For a Gibraltar-based retailer or reseller, most of your stock will already carry a barcode assigned by a UK, EU or wider supplier — your SKU is a second, entirely separate layer on top of that, built to suit how you organise your own shelves and spreadsheets, not how the manufacturer organises theirs.

SKU vs EAN, UPC, GTIN, serial and batch numbers

These terms get mixed up constantly, and the confusion causes real stock-control mistakes, so it's worth being precise. An EAN (part of the wider GTIN family) is a globally unique barcode number issued through a national GS1 organisation — for a Gibraltar business, typically via GS1 UK given the territory's close commercial ties. It identifies a product to any retailer and supplier on the planet. You can't make one up; GS1 licenses company prefixes and you assign numbers within your own block.

A SKU has none of that infrastructure. You invent it, it only has to be unique inside your own systems, and it can (and often should) encode information the EAN never will — which supplier you bought it from, which season it belongs to, or where it sits in your own category tree. Marketplaces call your SKU the "seller SKU" or "custom label" precisely because it's yours to define, layered on top of their own listing ID and any EAN the product carries.

Serial numbers are different again: they identify one individual unit (useful for electronics, tools and anything under warranty), while a batch or lot number identifies a production run. A SKU sits above both — one SKU can cover thousands of units across many batches and serial numbers.

Step-by-step: designing your own SKU naming convention

Worked example: category "Hoodie" → HOO, brand "Nova" → NOV, size "Medium" → M, colour "Charcoal" → CHR, giving HOO-NOV-M-CHR. Add a two-digit batch suffix if you restock the same combination from a different supplier later — HOO-NOV-M-CHR-02.

1. List the attributes that actually help you find stock fast. For most shops that's category, brand or supplier, size, and colour — resist the urge to add more than four or five, or the code becomes unreadable.
2. Decide an abbreviation rule per attribute. "Hoodie" might become "HOO" (first three letters), "Extra Large" might become "XL" (an initials rule), and a colour list might use a fixed custom mapping so "Charcoal" always shortens to "CHR", never "CHA" one week and "CHR" the next.
3. Pick one separator and stick to it. A hyphen is the safest universal choice — it survives copy-paste into Excel and most marketplace bulk-upload templates without being reinterpreted as a formula or a date.
4. Add a sequential number if two products could otherwise collide. Zero-pad it (001, 002…) so the codes sort correctly in a spreadsheet.
5. Decide on a maximum length before you generate anything. Marketplace fields have hard limits (see below), and a 40-character SKU isn't more informative than a 14-character one — it's just harder to read on a shelf.

Best practices — and the mistakes that come back to bite you

• Avoid the letter O and the digit 0 together, and the letter I or lowercase l next to the digit 1 — on a printed label these are genuinely hard to tell apart. This generator flags both automatically.
• Never start a SKU with a zero. Excel and Google Sheets silently strip leading zeros when a cell is treated as a number, turning "007-BLU" into "7-BLU" the moment someone re-opens your export.
• Don't encode information that changes — a supplier's cost price or a shelf location. Both change independently of the product itself.
• Keep the format identical across your whole catalogue. A SKU scheme that's 8 characters for one category and 14 for another looks fine until you try to sort a spreadsheet by SKU and the columns don't line up.
• Stick to A–Z, 0–9, hyphens, underscores and full stops. Spaces and special characters cause silent failures in CSV imports on most marketplace bulk tools.

Marketplace-specific SKU rules for Gibraltar-based sellers

Cross-border selling on Amazon.co.uk and eBay UK is the most common route for Gibraltar sellers, given the territory's trading relationship with the UK. Amazon's "Seller SKU" field allows up to 40 characters, and eBay's equivalent "Custom Label" field allows 50 — both are internal-only fields, never shown to buyers, and both strongly favour plain letters, numbers and hyphens over special characters, which have historically caused feed errors.

Because Gibraltar sits outside the EU customs union while trading heavily with both the UK and EU markets, sellers frequently list the same product across UK and EU marketplaces under the same internal SKU but different regional listing IDs — keeping one master SKU list, generated once here, avoids maintaining separate numbering schemes per marketplace.

Bulk workflow: from spreadsheet chaos to a clean variant matrix

The single biggest time cost in SKU management is entering size/colour combinations one at a time. If you stock 4 sizes and 5 colours across 3 styles, that's 60 SKUs — manageable in this tool in under a minute, because entering "S, M, L, XL" once against Size and all five colour names once against Colour generates every combination automatically as a true cartesian matrix, not a queue of single-item forms.

Once generated, sort the results table by any column to spot-check a size run, copy the whole set to your clipboard, or export to CSV or Excel. The Excel export writes every SKU as text, not a number, so codes with leading digits or hyphens import into your inventory system or a marketplace bulk-upload template exactly as generated.