Short definition SKU - Stock Keeping Unit
One SKU, abbreviation for stock keeping unit is a unique internal item number for identifying products in the warehouse. Unlike public barcodes, the SKU is particularly relevant for warehouses, ERP, shop systems and fulfillment. It helps companies precisely manage items, variants, and inventories. In short: The SKU creates order in the inventory.
It is used to:
- Clearly distinguishing between products
- Easy to manage variants
- To manage stocks correctly
- Pick & Pack-to control processes
- Allocate returns correctly
- Evaluate reports precisely
The cleaner the SKU system, the more efficiently the warehouse runs.
SKU example
An SKU is an individual code that companies themselves assign to control products internally.
Example: A t-shirt comes in three sizes and two colors. Although it is a product, several variants are created. Each variant usually has its own SKU. In this way, every single execution can be followed precisely.
example:
- TSHIRT-BLK-S
- TSHIRT-BLK-M
- TSHIRT-WHT-S
- TSHIRT-WHT-M
How does an SKU work?
An SKU is defined internally and in systems such as ERP, WMS, OMS or integrated shops. As soon as goods are stored, sold or returned, the movement takes place via this number.
In the warehouse, this means:
- Scanners recognize the SKU
- Picklists show the SKU
- Inventory is booked via SKU
- Reorders are planned according to SKU
The SKU is therefore the backbone of operational product management.
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Benefits of an SKU
Unique item identifiers
Each item and variant can be clearly identified.
Faster search
Employees find products more quickly in the warehouse and in the system.
Fewer mistakes
Mix-ups in sizes, colors, or bundles are reduced.
Better inventory control
Inventory levels can be precisely controlled for each variant.
Clean evaluations
Sales, returns or top sellers are precisely visible within the SKU.
Where is the SKU number?
The SKU number is usually not prominently visible to end customers, but internally in the respective systems.
Typical places:
- ERP system
- Backend shop system
- WMS /Warehouse management
- Product master data
- Picklists
- internal labels
- warehouse labels
- Product data feeds
Some brands also print the SKU on product labels or boxes.
What is the difference to EAN/ GTIN?
This is often confused — but it is important.
SKU
Internal item number, individually assigned by the company.
EAN/GTIN
Standardised global product identification for retail and scanning processes.
In short:
SKU = internal
EAN/ GTIN = externally standardized
A product can therefore have an SKU and a GTIN at the same time.
example:
- ITEM NUMBER: SHOE-WHT-42
- GTIN: 4061234567890
Typical mistakes with SKUs
Blurred variant assignment
Failures to separate colors, sizes, or sets result in shortages.
Too complicated number logic
Codes should remain structured but practicable.
Duplicate SKUs
Repeatedly assigned numbers create chaos in the warehouse.
Poor system maintenance
When shop, ERP and WMS use different SKU data, errors occur.
Historically developed game systems
Many companies are growing faster than their master data structure.
How should a good SKU be structured?
A good SKU is:
- unequivocally
- logically readable
- scalable
- system compatible
- short enough for operational use
example:
BRAND ABBREVIATION PRODUCT COLOR SIZE
Important: Clearly define once and use consistently.
