The documentation states “Projected Quantity is the level of stock that is predicted for a particular Item based on the current stock levels and other requirements”.
However it does NOT!
Suppose you have stock =0 and a purchase of 10 will arrive in 1 week. projected stock = 10.
If you get a customer order of 3 with requested delivery date in 4 days the projected quantity is 7 and thus implies you will not have any problems. However in real life you have, because you cannot deliver!!!
you have stock of 10. purchase leadtime of the product is 1 month. product cost price = 1000 USD per piece. you have a sales order for 1000 pieces to be delivered in 12 months.
The projected quantity will be -990. So this implies a problem !! the user will think he has to order but if he does now (witout using mrp) he will have spent 1000 * 1000 = 1.000.000 USD 11 month in advance.
So the projected quantity formula is incorrect !!
Wy is it incorrect: because it does not take into account the timing of all movements and reservation.
what should be in ERPNEXT:
- economic stock level in every movement and reservation
- avaliable to promise calculation
- capable to promise calculation
- Available to promise is: calculate if stock is available on the requested sales order delivery date.
This can either be done
1a) by using your :“Projected quantity” calculation BUT only taking into account stock, all movements and reservation between now and the delivery date !!
1b) Or registering in every move and reservation the calculated stock level at that moment (= economic stock level).
If you get a new sales order you can easily go to the movement/reservation of that date, look at the economic stock level and decide if enough stock is available.
a remark: only no problem will result for other customers if stock level at purchase lead-time date is also above 0!!
- Capable to promise:
this is used when not enough stock is available, it determines what the earliest date will be it will be available. So taking into account purchase lead-time, assembly times, etc.