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SAP Lot Sizing Procedures and MRP Parameters Reference

Lot sizing is the lever that decides how many planned orders MRP creates and how large they are. This reference lists the standard SAP lot size keys and the material master fields that control quantities, dates and exceptions, so you can read a planning result and know which field produced it.

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Key / field	Kind	Meaning	When to use / watch for
EX	Lot size key	Lot-for-lot order quantity	Order quantity equals the shortage. Good for expensive or low volume parts.
FX	Lot size key	Fixed lot size	Uses the fixed lot size BSTFE. Multiple lots are created if the shortage is larger.
HB	Lot size key	Replenish to maximum stock level	Order quantity fills up to the maximum stock level BSTMA. Common for reorder point planning.
TB	Lot size key	Daily lot size	Groups requirements for a day into one order.
WB	Lot size key	Weekly lot size	Groups requirements for a week into one order.
MB	Lot size key	Monthly lot size	Groups requirements for a month into one order.
PK	Lot size key	Lot size by flexible period length	Combines requirements across the number of days set by the period.
DISLS	Material master field	Lot sizing procedure key	Stored in MARC. Set on the MRP 1 view.
BSTMI	Material master field	Minimum lot size	Order quantity is raised to this value if lower.
BSTMA	Material master field	Maximum lot size	Orders above it are split into multiple lots.
BSTFE	Material master field	Fixed lot size	Used with the FX key.
BSTRF	Material master field	Rounding value	Order quantity is rounded up to a multiple of this value.
EISBE	Material master field	Safety stock	MRP plans to keep at least this stock. Triggers exception 96 if breached.
DISMM	Material master field	MRP type	Decides whether and how the material is planned.
PD	MRP type	MRP (requirements planning)	Standard type for deterministic planning on demand.
VB	MRP type	Manual reorder point planning	Reorder point triggers planning. Uses reorder level and lot size.
VV	MRP type	Forecast-based planning	Uses forecast values for requirements.
ND	MRP type	No planning	Material is excluded from MRP.
DISPO	Material master field	MRP controller	Groups materials for MD06 and MD07 lists.
DISGR	Material master field	MRP group	Drives planning parameters like strategy, horizons and exception handling.
BESKZ	Material master field	Procurement type	E in-house, F external, X both.
SOBSL	Material master field	Special procurement key	Subcontracting, stock transfer, phantom, and other variants.
PLIFZ	Material master field	Planned delivery time (days)	For external procurement. A major driver of MRP dates.
DZEIT	Material master field	In-house production time (days)	Used when no routing time is determined or for fixed lead time.
WEBAZ	Material master field	Goods receipt processing time (days)	Added after delivery or production for inspection and put away.
FHORI	Material master field	Scheduling margin key	Adds float before and after production and sets the opening period.
STRGR	Material master field	Planning strategy group	Examples: 10 make-to-stock, 20 make-to-order, 40 planning with final assembly.
Dynamic and optimizing	Concept	Part period balancing, least unit cost, Groff and similar procedures	Available in configuration, using cost inputs. Use only after testing against real demand.

Field names refer to the material master MARC data. Lot size key availability depends on configuration, so check your own system for additional or modified keys.

Test lot size changes safely

Optional: an expert review of how to simulate lot size changes against your demand data.

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How to use the reference

Open the material master MRP 1 and MRP 2 views and compare the fields to the reference. Search for a key like HB or a field like BSTRF to see what it does. Use the notes to decide whether a lot size procedure fits the part. Export the table to Excel to document planning parameters in a master data standard for your plant.

Compare lot size key with minimum and rounding values
Check planned delivery time before changing lot size
Document which keys are allowed per MRP group

Static lot sizing in practice

Exact lot size (EX) orders precisely the shortage and suits expensive or custom parts. Fixed lot size (FX) is natural when a process makes a standard batch. Replenish to maximum (HB) is common with reorder point planning. Period lot sizes (TB, WB, MB) group several requirements into one order and reduce setups and order count, at the cost of more inventory for early demand.

Other fields that change the order quantity

Minimum lot size raises small shortages to a minimum, maximum lot size splits large ones, and rounding value forces the quantity to a multiple such as a pallet or tray. Safety stock adds a buffer, and MRP type decides whether the material is planned at all. Together they explain most surprises, for example a planned order of 500 for a shortage of 120.

Common mistakes

Setting a high minimum lot size on a low runner builds excess stock. Using period lot sizes with long periods causes early orders and exception 15 messages. Ignoring rounding values in a unit of measure conversion creates odd quantities.

Review minimum lot size yearly
Use shorter periods for expensive parts
Check MRP type for materials that never plan

Frequently Asked Questions

What does lot size key EX mean in SAP?

EX is exact or lot-for-lot ordering. MRP creates an order for the net shortage, adjusted only by minimum lot size, maximum lot size and rounding value if they are maintained. It keeps inventory low but can create many small orders.

What is the difference between FX and HB?

FX creates orders in multiples of a fixed lot size defined in the material master. HB orders enough to fill stock up to the maximum stock level. FX suits fixed batch processes, while HB fits reorder point style replenishment.

Where is the lot size set in the material master?

The lot size key sits on the MRP 1 view in the field behind DISLS in table MARC. Minimum, maximum, fixed and rounding values are on the MRP 1 view and lot size data section, while lead time fields are in MRP 2.

Why did MRP create a bigger order than the shortage?

Most likely minimum lot size, rounding value or a period lot size key raised the quantity. Safety stock can also add to the net requirement. Check these fields on MRP 1 for the material.

If you want to test lot size changes before touching the material master, we can build a simulation over your SAP demand data that shows the effect on order count and inventory, read only.

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