BOM revisions
A new approved component list changes gross demand.
Manufacturing planning guide
What Is MRP? Bills of Materials, Shortages and Replenishment Explained
Material requirements planning calculates which components a manufacturer needs and when they are needed. A BOM defines quantities per assembly, while MRP compares demand to supply and highlights purchasing shortages.
MRP in plain English
Start with production demand, then calculate materials
For a 100-unit build, a bill of materials specifies four screws, two panels and one cable per assembly. Multiply those quantities by production demand: 400 screws, 200 panels and 100 cables. Now review available stock and on-time supplier receipts.
| Component | Gross requirement | Usable stock | On-time receipts | Net shortage |
|---|---|---|---|---|
| Screws | 400 | 240 | 100 | 60 |
| Panels | 200 | 175 | 0 | 25 |
| Cables | 100 | 120 | 0 | 0 |
The resulting shortage is 60 screws and 25 panels. This does not automatically tell the buyer how many to order: vendor minimums, packaging, lead times, reserves and approvals still matter.
Planning details
What causes an MRP plan to change?
Production dates
A delivery arriving too late may not cover the need date.
Inventory changes
New receipts, consumption or holds affect usable stock.
Supply changes
Delayed or reduced vendor receipts create new exceptions.
Straight answers
Frequently asked questions
Practical answers about how the software fits into day-to-day operations.
Is MRP the same as ERP?
MRP focuses on production material requirements, while ERP connects a wider set of business functions such as purchasing, inventory, sales, reporting and distribution.
Does a positive stock balance mean materials are available?
Not always. Some quantities may be reserved, restricted, damaged or needed for another order, so availability requires more than the total on-hand quantity.