In SAP Materials Management (MM), you can define several different units of measure (stockkeeping units) for each material, all of which are taken into consideration in Warehouse Management (WM).

The base unit of measure is the basis for inventory management and evaluation. Alternative units of measure, such as the order unit, issue unit or WM unit of measure, are defined to identify packages or containers for smaller units of measure such as cartons, boxes, bottles, barrels or pallets.

Quantities of warehouse materials (quants) are counted using the base unit of measure (UoM). Quantities in alternative units of measure are always converted to the base unit of measure for calculation purposes.

The stockkeeping unit is synonymous with the base unit of measure. In the SAP System, the term "base unit of measure" is more commonly used.

The WM unit of measure (WM UoM) is an alternative unit which can be defined in the Warehouse Management view of the material master record.

The unit of issue (UoI) is a unit of measure generally used in Inventory Management for processing goods receipts and goods issues.

Alternative units of measure can also be defined to identify packages or lager containers for smaller units of measure such as cartons, boxes, bottles, barrels, pallets (storage unit types) and so on.

The use of several different units of measure in the SAP system is useful, for example, for accounting, storage and packaging purposes. For example, if a crate contains several thousand pieces of a particular material, it is more expedient to purchase, package and sell this material by the crate or box rather than by the piece. Additionally, it is important to use units of measure that cause no field overflows to occur when the quantities are increased.

Additionally, in the WM view of the material master record, you can define a loading quantity for each pallet type or storage unit type (SUT). You can enter this quantity using any unit of measure that has been defined in the system.

The SUT is an important factor for the automatic stock placement strategy. The quantity to be putaway is divided by the quantity that is defined to fit on one SUT and is distributed for storage based on the strategy and capacity of the storage bins in the warehouse.

Since the MM system uses the base unit of measure for calculation purposes, the WM application requires that a conversion be defined for any alternative units of measure that have been assigned to a material.

When you create a new material in the system, for example, if you designate "piece" as the base unit of measure and "box" as an alternative unit of measure, the system will display a conversion window which asks you to define how many pieces are contained in a box.

The default unit of measure is the unit of measure that is selected by the system when you enter only a material number and quantity into the system. When you define a warehouse number you can designate primary and secondary default units of measure. These are then used by the system if you do not specify a unit of measure during a transaction. You enter them in the 1st default UoM field and the 2nd default UoM field in the Quantities/Weights section of the warehouse number record screen. If the primary default quantity unit is not maintained for a material, the secondary default quantity unit is used. If the secondary default quantity unit is not maintained for the material, the base unit of measure is used.

You confirm transfer orders using any unit of measure that is allowed for the material. The system converts this into the alternative unit of measure and stores it when the transfer order item is processed.

In the data fields 1st and 2nd default UoM in the warehouse number record, you can change the unit of measure proposed as a default by the system (i.e., if users do not enter a UoM). Units of measure from preliminary documents such as transfer requirements and deliveries are usually taken over by the system. Using the characteristic M, it is also possible to edit these documents automatically based on the WM unit of measure.

During the planning stage, the transfer of materials, and the subsequent display of warehouse stock, WM supports all related alternative units of measure for processing. For example, if the weight of a particular material is managed in kilograms, the system can make calculations based on the input of weight measures such as grams, ounces, pounds or tons.