A unit of measure is the code, such as PCS or BOX, in which an item quantity is expressed; each item has one base unit that all inventory entries are stored in.
A unit of measure defines how a quantity is counted: pieces, boxes, kilograms, hours. In Business Central every item has a base unit of measure, and all item ledger entries are recorded in that unit. Additional units are attached to the item with a conversion factor, the quantity per unit of measure, so a document line can be entered in boxes while inventory stays in pieces.
The global list is reached with Alt+Q and a search for Units of Measure, where each code has a description and an international standard code used by electronic documents. On the item card, the base unit sits on the General FastTab, and the item specific units with their conversion factor are opened through the units of measure action on the item. Separate fields let you set the unit that defaults on purchase lines and the one that defaults on sales lines.
Item BRG-1000 has base unit PCS and a second unit BOX with quantity per unit of measure 12. A purchase order line for 10 BOX at CHF 132.00 per box posts 120 pieces into inventory at CHF 11.00 each. A sales order entered as 2 PCS reduces inventory by 2, and the two documents remain comparable because both are stored in the base unit.
The classic error is a wrong conversion factor, for example 1 instead of 12, which inflates or deflates inventory by an order of magnitude and is only noticed at the next count. Changing the base unit of measure once transactions exist is another trap, since existing entries keep the old meaning and cost history becomes unreliable. Vendors who invoice in cartons while you stock in pieces cause constant quantity mismatches when the purchase unit of measure is not set on the item.
Unit conversion is where invoice automation most often breaks. Zentriq Document Capture reads the quantity and the unit printed on the vendor invoice and maps the line to the item, so the item reference and the purchase unit of measure need to be correct before automation is reliable; captured documents remain drafts that a person checks and posts. Non integer factors, such as kilograms per roll, deserve a deliberate rounding rule agreed with your accountant.
Not once entries exist for that item. Existing item ledger entries stay in the old unit, so the usual approach is to create a new item, or to add an alternative unit with the correct conversion factor.
Keep PCS as the base unit, add a BOX unit with the quantity per unit of measure, then set BOX as the purchase unit of measure and PCS as the sales unit of measure on the item.
Zentriq's AI tools automate many of the manual processes around unit of measure in Business Central. Learn about the Zentriq Agent or try Zentriq PunchOut to see how AI simplifies procurement in BC.