Replenishment Min/Max Calculator for SAP EWM and WM
An empty pick face stops a picker and often a whole wave. This calculator derives the minimum and maximum quantities for a fixed pick bin so replenishment starts early enough and the bin never overflows.
Your numbers
From the trigger to stock arriving in the pick bin, including task creation, travel and putaway.
Covers demand spikes during the response time.
Usually a case, layer or full pallet quantity.
Your results
Assumes steady demand. For erratic items, raise the safety margin or use statistical safety stock.
Minimum quantity vs response time
Sweeps Replenishment response time from 0.5 to 8, holding your other inputs fixed.
Pick face stockout analysis
An optional review of empty pick face events and replenishment delays from your warehouse task data.
Optional. The tool and every export work without this. No spam.
How to use it
Enter the daily demand for the item in pick units and the hours per day that picking happens. Then enter how long replenishment realistically takes from trigger to stock in the bin. Add a safety margin for demand peaks, the bin capacity and the quantity moved per replenishment. The result gives the minimum quantity that should trigger replenishment, the maximum, days of cover and how often replenishment will run. Check that the headroom between minimum and maximum is at least one replenishment quantity.
The formula
Demand per pick hour equals daily units divided by pick hours. The minimum equals that rate multiplied by response time and by one plus the safety margin, rounded up. The maximum is the capacity of the bin. The number of replenishments per day equals daily demand divided by the replenishment quantity. This is a classic reorder point model applied to a pick face, where the lead time is the internal replenishment response rather than a supplier lead time.
- Minimum = demand per hour x response hours x (1 + safety)
- Maximum = bin capacity
- Replenishments per day = daily units / replenishment quantity
Where it fits in SAP
In EWM, replenishment control for fixed bins uses minimum and maximum quantities on the product warehouse data, and the replenishment run creates warehouse tasks for the shortfall. In classic WM, fixed bin assignments with minimum, maximum and replenishment quantities in the material master storage type data drive the replenishment from reserve storage. Whichever you use, schedule the run frequently enough that the response time you entered is real, not wishful.
Common mistakes
The most frequent error is a response time based on the best case. If your replenishment tasks wait in a queue for a forklift driver, include that wait. Another is setting the maximum at a full bin when the replenishment quantity does not divide neatly, leading to partial pallets that block the face. Finally, do not use the same settings for fast and slow movers: re-run the tool per item class and slot the fastest items closest to the pick path.
Frequently Asked Questions
What if the minimum is bigger than the bin allows?
Then the bin is too small for the item's velocity or the response time is too long. Increase the bin size, shorten the response time or slot the item in a larger location.
How do I pick the safety margin?
Look at the highest hourly demand in recent weeks compared with the average. A margin of 20 to 30 percent suits steady items, while promotional or erratic items may need 50 percent or more.
Is this the same as safety stock?
No. Safety stock protects against supplier and demand variability at the warehouse level. This margin protects the pick face during the internal replenishment response time.
Can I use it for case flow racks?
Yes. Use the capacity of the lane as the maximum and the case quantity as the replenishment quantity.
If you want to find which pick faces ran empty last month and why, straight from your SAP task history, we can build that analysis on your own servers.
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