Guide · Methods
DDMRP vs MRP: what changes in day-to-day planning
Both plan material from the same bills of material and lead times. They differ in what triggers an order and how planners decide what matters most today.
Updated October 16, 2026
In short: MRP nets forecast and orders against stock through every level of the bill of material and plans each item by date. DDMRP places stock buffers at chosen points, sizes them from average daily usage and lead time, and orders when an item's net flow position drops into its yellow zone. Planners then work from buffer status instead of due dates.
How MRP plans
Material requirements planning starts from a master schedule built from forecasts and customer orders. It explodes the schedule through the bill of material, nets each component against stock and open orders, and offsets by lead time to get planned orders with dates. When anything upstream changes, such as a forecast revision or a late order, MRP recalculates and issues reschedule messages down every level that depends on it. Plans built this way inherit the error of the forecast, and frequent small changes can produce a stream of messages, often called nervousness.
What DDMRP changes
Demand Driven MRP was introduced by Carol Ptak and Chad Smith in the third edition of Orlicky's Material Requirements Planning (2011) and is promoted by the Demand Driven Institute. It keeps the bill of material and much of MRP's netting logic but adds five components:
- Strategic inventory positioning: choose where to hold stock so lead times between those points are shorter.
- Buffer profiles and levels: size red, yellow and green zones from usage, decoupled lead time and variability.
- Dynamic adjustments: recalculate buffers as usage changes and plan known changes ahead.
- Demand-driven planning: order from net flow position (on hand + on order − qualified demand).
- Visible and collaborative execution: manage open orders by buffer status and on-hand alerts.
Side by side
MRP and DDMRP compared
| Aspect | MRP | DDMRP |
|---|---|---|
| What triggers an order | A projected shortage on a date | Net flow position at or below the top of yellow |
| Demand used for orders | Forecast plus customer orders | Actual orders that qualify (past due, today, spikes); usage sizes the buffer |
| Lead time | Cumulative lead time through the bill of material | Decoupled lead time between stock buffers |
| Stock policy | Safety stock per item, often a fixed quantity or days | Buffers at chosen decoupling points, sized by profile |
| Planning priority | Due date | Buffer status: net flow as a % of the top of green |
| Reaction to change | Reschedules every dependent level | Buffers absorb variation; only items near or below the top of yellow get new orders |
| Execution signals | Exception and reschedule messages | On-hand alerts against the red zone |
Where MRP still fits
- Make-to-order and engineer-to-order work with firm orders, long lead times and little repeat demand. There is no steady usage for a buffer to cover.
- Items between buffers. Inside DDMRP, unbuffered parts are still planned with MRP-style netting; the explosion simply stops at buffered positions.
- Scheduled, predictable demand such as a fixed delivery schedule may need date-based planning more than a buffer.
In practice many companies run both: buffers for the items where variability and long lead times cause the most trouble, and MRP for the rest. Some ERP systems offer DDMRP features natively or through add-ons; others need a separate tool or a spreadsheet.
How to try DDMRP without changing your ERP
- Pick 20 to 50 stocked items that cause frequent shortages or carry visible excess.
- Export their usage history, lead times, MOQs and current stock, and size buffers with medium factors as a starting point.
- Compare each buffer's average on-hand target (red + half of green) with today's stock to see where you hold too much or too little.
- Plan those items from net flow position for a few weeks alongside your usual process, then tune the factors.
The free planner does steps 2 to 4 in your browser from CSV exports. The guides on buffer zones, net flow position and average daily usage walk through the math. This site is independent and not affiliated with or endorsed by the Demand Driven Institute.