ERP & MRP Planning calculator
MRP Material Requirements Calculator
MRP Material Requirements helps planners convert demand from sales orders, forecasts, or parent work orders into the net quantity that still needs to be purchased or produced. It focuses on the same part number, revision, location, and planning bucket so the requirement is not overstated.
What this calculator does
- Calculate net material requirements from gross demand, on-hand inventory, scheduled receipts, and other usable supply.
- an MRP planner needs to decide how many components or finished units still need planned supply
- It calculates the net quantity still required after usable supply is applied to gross demand.
Formula used
- Net material requirement = gross material requirement - available on-hand inventory - open receipts - approved substitute or reserved supply
- Total usable supply = available on-hand inventory + open receipts + approved substitute or reserved supply
Inputs explained
- Gross material requirement: Use demand from sales orders, forecast consumption, dependent BOM demand, or released parent production orders.
- Available on-hand inventory: Use inventory that is net of quality holds, blocked stock, cycle-count adjustments, and existing hard allocations.
- Open PO or work-order receipts: Include firm scheduled receipts expected before the requirement date.
- Approved substitute or reserved supply: Include only substitute stock, transfer orders, or reserved supply approved for this requirement.
How to use the result
- Use it during ERP cleanup, MRP review, production scheduling, S&OP prep, purchasing decisions, shortage meetings, capacity planning, or daily shop-floor execution reviews.
- This is a planning estimate. Confirm final commitments against current ERP/MRP records, released BOMs and routings, inventory accuracy, supplier commitments, open work orders, quality holds, and shop-floor constraints.
Common questions
- What is the MRP Material Requirements calculator for? It calculates the net quantity still required after usable supply is applied to gross demand.
- What information do I need before using it? You need gross demand, usable on-hand inventory, open receipts, and approved substitute or reserved supply.
- How should I use the result? Use the net requirement to create, resize, or cancel planned purchase orders, transfer orders, or production orders.
- When is the result only an estimate? It is only an estimate when demand, inventory, lead time, routing hours, setup time, yield, supplier dates, or work-center capacity comes from forecast assumptions or stale ERP data instead of current orders and recent execution history.
Last reviewed 2026-05-12.