Purchasing in Different UoM
Every item in ERPNext is linked with a Stock Unit of Measurement (UoM). This Stock UoM determines how the quantities of the item are to be stored and handled in inventory.
For instance:
- The UoM of a pen may be Nos (Numbers).
- The UoM of sand may be Kg.
But while ordering a purchase from a Supplier, the UoM can be different from the Stock UoM.
- Example: Pens can be bought in Boxes rather than in separate Nos.
- Sand can be bought in Truckloads while stocked in Kg.
ERPNext enables buying in various UoMs while keeping stock in the Stock UoM using UoM Conversion Factors.
Scenario
Item Pen is held in Nos, yet bought in Box. Therefore, a Purchase Order will be generated for Pen in Box.
Step 1: Edit UoM in the Purchase Order
In Purchase Order, there will be two UoM fields for each item:
- UoM – Shows the Purchase UoM utilized in the transaction.
- Stock UoM – Shows the default UoM in which the item is kept in stock.
The Stock UoM of the item is loaded by default in both the fields.
- You must fill the UoM field with the Purchase UoM (Box here).
- The Stock UoM does not change (Nos).
This guarantees that:
- The supplier can view the ordered amount in the Purchase UoM in the printed format.
- Internally, ERPNext itself converts it into Stock UoM for inventory tracking.
Step 2: Update UoM Conversion Factors
How the Purchase UoM and Stock UoM relate must be specified using a Conversion Factor.
For instance:
- If 1 Box = 20 Nos, then UoM Conversion Factor = 20.
When you enter a quantity of 1 Box in the Purchase Order:
- The system calculates the stock automatically as 20 Nos in the Stock UoM.
This maintains correct stock valuation and inventory movement.
Stock Ledger Posting
Regardless of whatever Purchase UoM is chosen, all stock ledger postings are always in the Stock UoM of the item.
- Example: When 1 Box of Pens is bought and the conversion factor is 20, the stock ledger will adjust inventory by 20 Nos.
Important: You need to set the conversion factor correctly; otherwise, stock balances and valuation will be incorrect.
Set Conversion Factor in Item
To prevent manually entering conversion factors in each transaction, you can predefine them in the Item Master.
- In the Item master, in the Purchase Details tab, you can define all possible Purchase UoMs of the item.
- Each Purchase UoM must have its Conversion Factor mapped with the Stock UoM.
For instance:
- 1 Box = 20 Nos
- 1 Carton = 200 Nos
This enables ERPNext to automatically apply the proper conversion in all purchase transactions, and brings consistency and accuracy to the entire system.