Unit of Measure Definition
A unit of measure (UoM) is the standard unit used to express how a product is measured, counted, or sold, such as kilograms, litres, metres, pieces, or boxes. It gives every quantity a clear meaning: "5" on its own says nothing, but "5 kg" or "5 boxes" does.
What types of units of measure are there?
Units of measure fall into two broad groups:
- Measurement units describe physical properties of a product, such as weight (g, kg, lb), length (mm, cm, in), volume (ml, l, gal), or area (m², ft²).
- Packaging and trade units describe how a product is counted, bought, or sold, such as piece, pair, pack, box, carton, or pallet.
A single product often uses both. A tile might have a measurement of 30 × 60 cm, be sold by the square metre, and ship in boxes of 1.44 m².
What are base, sales, and purchase units?
Businesses often handle the same product in different units at different stages:
- Base unit: the smallest unit the business tracks in its systems, for example one bottle
- Purchase unit: the unit used when buying from a supplier, for example a case of 24 bottles
- Sales unit: the unit customers buy, which may be a single bottle online and a full case for wholesale buyers
Conversion factors link these units (1 case = 24 bottles), so stock, prices, and orders stay accurate no matter which unit is used. Sales units are also closely tied to the minimum order quantity, especially in B2B.
Why does the unit of measure matter?
Unclear or inconsistent units cause real, costly mistakes. A customer orders "1" expecting a box of 100 screws and receives a single screw. A supplier sends weights in pounds that get imported as kilograms. A marketplace rejects a listing because the dimensions use the wrong unit. These problems lead to incorrect orders, returns, pricing errors, and compliance issues, since many countries require unit prices such as price per kilogram or per litre.
To avoid confusion between systems and trading partners, many businesses use standardized unit codes, such as those defined in UN/ECE Recommendation 20 (for example, KGM for kilogram, MTR for metre, and H87 for piece).
How are units of measure managed in product data?
In spreadsheets, units are often typed as free text, so "kg," "Kg," "kilo," and "kilogram" all appear in the same column. A Product Information Management (PIM) system avoids this by attaching a unit to each numeric attribute and limiting it to a defined list of values. Many PIM systems can also convert between units automatically, so the same product shows centimetres and kilograms to European customers and inches and pounds to US customers, without anyone maintaining both sets of values by hand.
