ERP & MRP Planning calculator
Inventory Policy Days Calculator
Inventory Policy Days converts stocking policy into days of supply using current usage and risk assumptions.
What this calculator does
- Estimate protected inventory days from usable on-hand quantity, daily usage, and policy risk factor.
- an inventory planner needs to check whether stock policy covers demand
- It estimates days of supply protected by the current inventory policy.
Formula used
- Protected inventory days = usable on-hand quantity ÷ average daily usage ÷ inventory policy risk factor
Inputs explained
- Usable on-hand quantity: Use inventory available for demand after allocations, quality holds, blocked stock, and cycle-count corrections.
- Average daily demand or usage: Use forecast consumption, recent issues, or MRP demand for the item.
- Inventory policy risk factor: Use 1.0 for normal policy, or greater than 1.0 to reserve extra days for risk.
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 Inventory Policy Days calculator for? It estimates days of supply protected by the current inventory policy.
- What information do I need before using it? You need usable on-hand inventory, average daily usage, and policy risk factor.
- How should I use the result? Use it to tune safety stock, reorder points, and service-level assumptions.
- 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.