Inventory basics

How to Create a Correct SKU

A Short Guide to SKUs

By Jacek Jarecki

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What is a SKU?

SKU (Stock Keeping Unit) is a unique alphanumeric code assigned by the seller to a product or specific listing in order to manage the catalogue and stock. It is the seller's internal identifier - not a global product number. On Amazon, you can create your own SKU or use one generated by the system.

A good SKU should be easy for a person to read, logically structured and easy to sort.
Comparison of random-looking SKU codes with clear, structured SKU codes
A random-looking code may work technically, but a well-designed SKU lets you recognise the product without checking a separate reference table.

SKU vs other identifiers

EAN / GTIN A global product identifier. It does not depend on the seller or marketplace.
ASIN Amazon Standard Identification Number - a 10-character product identifier in the Amazon catalogue. Listings for the same catalogue product use the same ASIN.
SKU Your code for a specific listing or stock item. One ASIN can have several SKUs for the same seller, for example separate SKUs for merchant-fulfilled and FBA offers.
FNSKU Fulfillment Network Stock Keeping Unit - Amazon's identifier for FBA inventory associated with a specific seller. It helps distinguish that seller's units from inventory belonging to other sellers.

01

Building a SKU: from broad to specific

The simplest system is usually the best: each part of the code should have one fixed meaning.

Base example

LODUN-NAVY-098

LO DUN NAVY 098
BrandLOVRAIN ProductDungarees ColourNavy Size98 cm

Why this order?

The code starts with the broadest information and then moves towards the details. This naturally groups variants from the same product family together, while the SKU itself can be understood without opening the product page.

1. Brand / line
A short, fixed code. Example: LO = LOVRAIN.
2. Product type
Create one consistent code dictionary: DUN = dungarees, JAC = jacket, etc.
3. Variant
Colour or another attribute that you actually distinguish in the catalogue. Example: NAVY.
4. Size
A value always written in the same format. Example: 098, 104, 110.

The separator is part of the system too

A hyphen greatly improves readability and works well across marketplaces, CSV files and Excel. The key is to use the same separator consistently throughout the catalogue.

One part of the SKU = one meaning. Do not change what a code means halfway through the catalogue.

02

Sorting: a small detail that makes a big difference

The key rule: if your SKU contains numbers, design them to use a fixed length.

Why?

In many reports, spreadsheets and systems, a SKU is treated as text. This means the software compares characters from left to right rather than always interpreting the numeric value the way a person would. A fixed field length removes this problem and makes sorting predictable.

NO YES
LODUN-NAVY-92LODUN-NAVY-092
LODUN-NAVY-98LODUN-NAVY-098
LODUN-NAVY-104LODUN-NAVY-104
LODUN-NAVY-110LODUN-NAVY-110

How many digits should you use?

Look at the largest value you realistically expect in that field. If sizes go up to 134, use a three-digit field, so write 092, 098, 104, 110. If you are designing a field that may run from 1 to 9999, use four digits: 0001, 0002.

This is not only about sizes.
The same principle applies to model numbers, lengths, variant numbers and any other numeric field you may want to sort later.

What about S / M / L sizes?

You do not need to convert everything into numbers. Consistency matters most. If the order S, M, L, XL matters when sorting, you can add a sequence number, for example 01-S, 02-M, 03-L, 04-XL.

03

Prefixes: FBA, merchant and condition

The base SKU should describe the product. Add a prefix when it helps distinguish how the same product is handled.

Base SKU and FBA

SKUMeaning
LODUN-NAVY-098base SKU / merchant (FBM)
FBA-LODUN-NAVY-098the same product as an FBA offer
MER-LODUN-NAVY-098optional: merchant in a catalogue that historically started with FBA

Why I prefer a prefix

When sorted, all codes beginning with FBA- fall into one block. In practice this is useful because FBA and merchant offers are handled differently: stock is managed differently, fulfilment processes differ, and reporting workflows are often separate.

This is the author's preference, not a universal rule. If you prefer all versions of the same product to stay together, you can use a suffix instead, for example LODUN-NAVY-098-FBA. Consistency matters most.

Condition - only when it differs from the default

If your standard offer is New, there is no need to add NEW to every SKU. Encode the condition only when a specific offer differs from the default.

VG-LODUN-NAVY-098your own abbreviation: Very Good
ACC-LODUN-NAVY-098your own abbreviation: Acceptable
FBA-VG-LODUN-NAVY-098FBA + condition + product

Note: abbreviations such as VG and ACC are part of your own SKU system. Amazon does not require these particular abbreviations in a merchant SKU.

04

Rules that keep a catalogue organised

A good SKU system does not need to be complicated. It needs to stay consistent and understandable years later.

Create a code dictionary and keep it consistent
If NAVY means navy blue, do not later use NAV, DARKBLUE and NB for the same colour.
Do not encode data that changes frequently
Price, current stock level, supplier or promotion should generally not be part of a permanent SKU.
Avoid spaces and random characters
Simple letters, numbers and one separator are easier to work with in CSV files, Excel, integrations and marketplaces.
Design the system before the catalogue grows
A few minutes of planning with 20 products can save many hours of clean-up when the catalogue reaches 2,000 products.

Example LOVRAIN system

LODUN-NAVY-092Dungarees, navy, 92
LODUN-NAVY-098Dungarees, navy, 98
LODUN-NAVY-104Dungarees, navy, 104
FBA-LODUN-NAVY-098The same variant as FBA
VG-LODUN-NAVY-098The same variant in a different condition

Quick checklist

  • Can I tell what the product is from the SKU alone?
  • Do all parts of the code always mean the same thing?
  • Do numeric fields have a fixed length and sort correctly?
  • Are colour, product and size names standardised?
  • Does an FBA / condition prefix add genuinely useful information?
The best SKU is not the shortest code. It is the code that stays understandable as the catalogue grows.

05

Examples of well-designed SKUs

Three different products, one principle: a SKU should be short, readable and consistent.

Galleksa - Invisible Bookshelf

GALIB-WHT-03

GALLEKSA-IB-WHITE-03

Galleksa Invisible Bookshelf, white, 3-pack. Both codes are understandable, but the shorter version is more convenient in day-to-day work.

GAL = Galleksa | IB = Invisible Bookshelf | WHT = White | 03 = 3-pack

Nike - Air Force 1

NI-AF1-WHT-43

NIKE-AF1-WHITE-43

Nike Air Force 1, white, EU size 43. Both SKUs communicate the same information; the first is simply shorter.

NI = Nike | AF1 = Air Force 1 | WHT = White | 43 = EU size 43

Adidas - T-shirt

AD-247-BLK-XL

ADIDAS-247-BLACK-XL

Adidas T-shirt, model 247, black, size XL. With letter-based sizes, you can additionally use a sequence number if correct sorting is important.

Sorting: AD-247-BLK-01-S | 02-M | 03-L | 04-XL | 05-XXL

A SKU should be as short as possible while still remaining clear enough to understand.

The Nike and Adidas examples are sample seller SKUs created for this guide; they are not official manufacturer codes.

Amazon terminology: ASIN and FNSKU are described in line with Amazon Seller Central / Sell on Amazon materials, current as of September 2026.

About this guide: This guide was developed from more than 10 years of practical e-commerce experience, including selling on Amazon, eBay and Etsy. The principles are based on day-to-day work with product catalogues, variants, FBA and merchant offers, and SKU management across multiple sales channels.

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