Material Requirements Planning (MRP)

Material Requirements Planning (MRP)


What is Materials Requirements Planning (MRP)?

Material Requirements Planning (MRP) balances supply and demand for purchased and manufactured items. Given a set of demands or requirements, MRP automatically calculates a time-phased schedule of planned supply orders or replenishments to satisfy those demands. Material Requirements Planning (MRP) looks at demand for finished items and uses product structure information / Bill of Materials (BOM) to calculate demand for component items.


For each item in the BOM, Material Requirements Planning (MRP) looks at the ordering information, the Quantity currently on hand and lead time to procure or manufacture, and generates planned orders suggesting how many of that item to buy or make and when to do so.


It takes demand from sources such as current and forecast orders, work orders, and parts below safety levels, subtracts supply, in the form of inventory on hand, on order, or in process, and calculates requirements for ordering or building parts to cover that demand.

Demand generated Supply Output
Confirmed Sales Orders with Due date to delivery the items Purchase Orders with Due date of delivery Planned Purchase Indents
Forecast Confirmed Work Orders with Delivery date to deliver Planned Work Orders with dates to deliver.
Stocks that have gone below “REORDER Level”

Net quantity on hand (QOH) / Minimum Ordered Qty.

Planned Work Order that’s created manually.
Master production schedule (MPS)


Material Requirements Planning (MRP) is a key manufacturing planning process that uses all sources of demand and supply to:

  1. Calculate gross item requirements and projected on-hand inventory
  2. Schedule and plan orders


Running an Material Requirements Planning (MRP) for production

There are two modes of MRP

  1. Regenerative MRP – plans for all items at selected sites.

It recalculates demand and plans supply for all items. The first time you run MRP, it should be regenerative.

  1. Selective MRP– Prepare the plans only for items that have been selected.


Types of Data considered for Material Requirements Planning (MRP)

Need to capture the below items based on which the ORDER due date is calculated. To effectively run Material Requirements Planning (MRP) certain information relating to parts should be established. Since Material Requirements Planning (MRP) calculates the quantities to purchase or make based on this data, it is important to ensure that these parameters are maintained properly.




1 Location Where this item is Stored? Typically in factories or warehouse, we store the materials in Racks, Floor etc. If a location is considered as a “SCRAP”, then the items in this location shouldn’t be considered.
2 Purchase / MFG / Configuration (P/ M / C) Planning (MRP) uses the Purchase / Manufacturing code to distinguish manufactured items from purchased items. This is important for MRP to raise a Work Order or a Purchase Indents.
3 MRP Required? Whenever the stock goes below REORDER level, we are generating the ALERTS on dashboard.
4 EOQ or Economic Order Quantity This is the minimum quantity for which MRP will plan an order. If MRP determines that there is a need for a quantity of 22.5KG for a part, but that part has an EOQ of 50KG then MRP will recommend that an order for 50 is created.

This is only for Purchase type of Items (P) and not for anything else.

5 Order Quantity in multiples of When the Purchase Indent is raised, it would be in multiples of this. This allows you to create orders in even multiples. As an example, if MRP determined there was a need for a quantity of 135 KG for a part, and the multiples was set to 50, MRP would create a planned order for 150, which is the next highest even multiple to cover the requirements.
6 Shrinkage / Loss Factor / Scrap % A percentage value that’s used to cover expected scrap or other loss during the delivery or production
7 Purchase / Procurement Lead time Days required buying the items from Supplier (Only for P items). MRP uses this in scheduling recommended orders.
8 Manufacturing Lead time The number of working days it takes to manufacture an item, including the time it takes to process paperwork, issue components, Inspect the finished product, and receive it into stock.
9 Quality Lead time The number of working days it takes to inspect a purchased item after it is received
10 Subcontracting lead time This is used for the Subcontracting operations and this time is added based on the SC operation in a ROUTING stage.
11 Round off Decimals and based on this, the QTY ordered and how its kept is controlled (0,1, 2, 3)
12 BOM BOM which is used to explode the RM and WIPs
13 Routing ID To identify the Work center and work loads
14 Key Item If this item is part of a BOM, then we cant produce the FG unless this item is available and is issued.
15 The start day of the Week.
16 Working days in a week This helps to arrive at the total working days in a week
17 Duration for Order Release dates How many days before we have to release the Orders for Production or Purchase`
18 MRP Horizon Material Requirements Planning (MRP)’s MRP horizon is how far to plan forward in time, and is determined by how far ahead demand is known and by the lead times through the manufacturing operation.

For example, we have confirmed SO up to next four months. Question is do we need to consider the Orders for the next four months for the planning or just consider for a month.


MRP Scheduling / Planning

For materials that are planned according to the Material Requirements Planning (MRP) and forecast-based planning procedures, the requirement dates in the future are known. Scheduling is always done in Backward schedule mode and if the dates falls short then its Forward Scheduled.

  1. Backward scheduling – Schedule the dates based on due date to deliver the items and then we plan backwards from that date onwards such that the starting date should be greater than or equal to TODAY. If we don’t meet the deadlines, then we go for Forward Scheduling
  2. Forward scheduling – In this approach, we start the delivery planning starting from today and we look at when the overall delivery can happen.


Backward Scheduling Process Flow

 The system calculates the Goods Receipt Time backwards using the requirements date and thus determines the Order finish date. The system calculates the in-house production time backwards using the order finish date and thus determines the order start date. The system calculates the opening period backwards using the order finish date and thus determines the order opening date.

The system always determines the basic dates for planned orders using Backward Scheduling. The system automatically switches to forward scheduling if the determined start date lies in the past (<Todays date).


Product Delivery / Requirements date 25 June (Friday)
Procurement Duration 1 day (workday)
POR Inspection LT 1 day (workday)
In-house production time for the material 6 days (workdays)
Order Release days 6 days (workdays)
Workdays = Monday to Friday, no holidays in between


Scheduled Dates to release the Order Date

  1. Requirements date minus Procurement time + Goods Receipt items Inspection Lead Time= order finish date

25 June. (Friday) minus 2 workdays = 23 June (Wednesday)

  1. Order finish date minus in-house production time= order start date

23 June (Wednesday) minus 6 workdays = 15 June (Tuesday)

  1. Order start date minus Order Release dates = Order opening date

15 June (Tuesday) minus 6 workdays = 7 June (Monday)


Forward Scheduling

Materials that are planned using Material Requirements Planning (MRP) or Forecast-based planning are switched to forward scheduling if the start date calculated in backward scheduling was in the past.The system determines the date by which the material will be available again, starting from the material shortage date.

In forward scheduling, the opening date is of no significance as the ordering process is started immediately.


Material shortage date 01 June (Friday)
Procurement Time 10 day (workdays)
Purchase Inspection LT 1 days (workdays)
Workdays = Monday to Friday, no bank holiday

Material shortage date plus Procurement time plus POR Inspection LT = delivery date

01 June (Friday) plus 10 calendar days +1 workday  = 14 June (Thursday)


Calculating the Dependent Requirements Date 

As the components and the assemblies are needed for the production of a higher-level planned order, they must be available by the order start date of this higher-level planned order.

If no lead-time offset has been maintained, the system uses the order start date for the source planned order as the dependent requirements date for the components

  1. Calculating Procurement Quantity (Purchase Quantity) – Material Requirements Planning (MRP) raises the planned orders and this needs to be approved to convert them into Purchase indents.

The system determines material shortages for requirement dates in the net requirements calculation. Receipts must now cover these shortage quantities. The system calculates the receipt quantity, which is carried out during the procurement quantity calculation.

Application would use the parameters set in Product Planning module like EOQ, Multiples Of, Scrap %age, Procurement Lead Time, Inspection LT, Round off, Lead time offset parameters

  • The system adjusts the determined shortage quantities to match the parameters of the required EOQand thus determines the order quantity (In case of Purchase)
  • If you have made an entry for scrap, the system calculates the scrap quantityand settles this against the total quantity.
  • If you have defined a round off value, the system rounds up the lot size and thus calculates the procurement quantity.

Final Quantity = Round off (Required QTY * (1 + scrap %age), 0)


  1. Calculating Production Date and Time – This generates the WORK ORDER to produce the items.

Routing ID for the material is a must is added into Product Planning Parameters. The production start dateand the production finish date, are specified for materials that are produced in-house.

The production datesare determined using the Routing. The system hereby uses the TIME DURATION that are allocated to the material. These Durations are “before production” and “after production” duration and so on.

The system normally executes the time scheduling with backwards scheduling and starts from the determined order finish date. The system only switches to forward scheduling and starts from the order start date, if the times in routing are substantially shorter than the times in the material master and the determined production start date is therefore further in the future than necessary.

  • The system determines the production finish date. Starting from the production finish date, the individual operations of the routing are then scheduled backwards. The starting date of the first operation is the production start date. (Routing is the basis for this)
  • The Timeduration before productionis the number of workdays that are planned as a buffer between the order start date and the production start date. By using this float, delays in material staging do not cause delays in starting production. Additionally, if there are capacity bottlenecks or delays in an incoming sales order, the production dates can be brought forward.


Bill of Materials (BOM)

Materials may appear in several products and in several production levels of a product. The low-level code represents the lowest level of usage of a material within all product structures.

It determines the sequence in which the materials are planned. The system plans materials with the low-level code 0 first and then those with 1 and so on. The lower the low-level code is, the higher the number assigned to the level.

The BOM is exploded and the dependent requirements are determined within MRP during the planning run, after the system has performed the procurement quantity calculation and scheduling.

The bill of material is exploded for every new procurement proposal for an assembly during the planning run.

Dependent requirements, which mean the required quantities, are determined for all the assemblies and components needed to produce the product. The system determines the valid BOM that is to be used for the explosion and for determining the dependent requirements.


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