In modern logistics facility planning, layout design relying on experience and intuition is no longer viable. The center scale calculation of a distribution center is a complex combination of additions and subtractions repeating the movement and storage of cases and pieces, and this must be unraveled using mathematical models.
During the calculation process, depending on the objective (which area is being designed), the base unit changes continuously from retrieval count, piece count, case equivalent, and PL (pallet) equivalent, to volume equivalent and weight equivalent. Tera Calculation 2 integrates the individual calculation logic of each site and, by starting from the average of all data (Tera setting), it enables the theoretical calculation of inventory and receiving volume. It logically calculates a sequence of optimal scales, from receiving to the shipping space area and number of berths, storage space, and ultimately the building area and site area.
In the data processing for the center scale calculation, Tera Calculation 2 focuses particularly on pallet storage efficiency in the storage space, actively adopting the "PL equivalent (pallet equivalent value)" as the key metric for rank setting.
💡 Two Important Reasons for Adopting the "Overall Average" in Shipping Data
1. Complete prevention of calculation omissions: If analysis is performed by selecting only specific shipping days (such as busy days at the end of the month), items that coincidentally had no shipping records on that day (e.g., long-tail products) will be entirely omitted from the calculation. By adopting the overall average, the necessary storage space for all items can be accurately comprehensively covered.
2. Prevention of overinvestment (over-spec): If the center scale calculation is performed based on the maximum peak day, an unnecessarily huge building and equipment will be calculated, resulting in the continuous payment of wasteful depreciation expenses. As a basic principle of logistics, the excess volume during peak times should be covered by "operations" such as utilizing safety stock or advance shipping, and it is an ironclad rule to match the hardware scale to "average stable operations."
Based on this principle, Tera Calculation 2 strictly separates and calculates the traffic lines for case shipping and piece shipping. By saving and deploying as many as 32 aggregation tables (including converted values) within the Access system, it enables multifaceted and flexible verification simulations.
The most common trap in logistics facility planning is "performing area calculations by merely trusting the current inventory data (WMS actual values) as is." Because actual values include wasteful stagnant inventory and stockouts, it is extremely important to perform a theoretical calculation of proper inventory and receiving volume from correct shipping data and comparatively verify it against the current actual values.
Based on the required inventory per item (PL equivalent) calculated from the shipping data, the loading format onto a pallet is automatically determined. By meticulously categorizing whether it is a "Single PL" where one item fills the pallet, or a "2 to 8 Mixed PL" where multiple small-lot items share a pallet, it calculates an extremely accurate number of required pallets aligned with the realities of the site, directly linking this to the area of the storage space.
When performing the theoretical calculation of inventory and receiving volume, the required area changes drastically depending on how the "timing of receiving" is set. By running simulations that intentionally disperse the receiving dates of each item on the system according to fluctuating inventory days (for example, ordering on a 6-day cycle), it is possible to suppress the peak (maximum volume) of the total inventory of the entire distribution center, ultimately minimizing the required building area.
Furthermore, it automatically determines the optimal packaging format based on the receiving volume per item (e.g., pallet-unit receiving if 0.5 PL or more, or piece-unit Oricon receiving if 0.5 cases or less) to accurately estimate the total volume of goods unloaded from trucks.
Unlike shipping, receiving operations are relatively easy for the company to control in terms of ordering (specifying and dispersing delivery dates and times). Therefore, by scheduling the receiving space to share the time zones when the shipping space area and number of berths are vacant, it becomes possible to significantly reduce the dedicated receiving space, directly leading to cost reduction.
Securing the shipping space area and number of berths is the last line of defense to prevent delivery delays. It is a critically important space where case goods retrieved from the storage space, and piece goods after picking and assorting, are consolidated by destination, and where "cargo staging and retention" takes place until they are loaded onto trucks after shipping inspection and packing are completed.
The shipping work space is the heart of the center where the most personnel are deployed and directly impacts productivity. The areas for the destination sorting space for case goods, picking racks for piece shipping (flow racks, medium-duty racks), and packing lines are meticulously calculated.
Calculates the area of the reserve area (storage space) needed to store the remaining large-lot volume, which is determined by subtracting the inventory already replenished in the shipping work space (flow racks and medium-duty racks) from the total inventory volume of the entire center.
⚠️ The 5m Standard and the "Virtual Floor" Rule under the Fire Service Act
If the bottom of the goods stored on the top tier of a pallet rack exceeds a height of 5,000mm (5m), it is deemed under the Building Standards Act and the Fire Service Act that a "virtual floor" exists there, which triggers the obligation to add sprinklers and strictly install firewalls, so utmost care is required when setting rack heights.
To determine the total area, the following ancillary areas essential for the operation of the center are added to the sum of the pure operational areas calculated so far (receiving/shipping space area and number of berths, shipping work space, and storage space).
Specifically, this includes adding the office area where the center manager and clerks are stationed, welfare areas such as break rooms and locker rooms for workers, storage areas for materials/sub-materials consumed in large quantities (unfolded cardboard, tape, cushioning materials, forms), and main aisles (arteries like 4m width) where forklifts can safely pass in both directions. Furthermore, it performs a negative adjustment as a reduction factor for the overlapping space that can be shared between receiving and shipping depending on the time zone, calculating a precise, waste-free total floor area.
Once the required area inside the warehouse is finalized, the process moves on to calculating the building as the hardware enclosing it, and then calculating the land.
Performs a simulation of the building area that will become the vessel of the logistics center. The optimal building volume is determined according to land constraints and the investment budget.
The final site area is not simply sufficient as long as the building fits inside. A vast external space is indispensable for trucks to enter and exit safely and smoothly, and to harmonize with the surrounding environment.
In addition to the building projected area viewed from directly above, the required site area is finalized only after adding all of the following: turning aisles where large trailers (16m class) can dock without reversing (securing vehicle width + 1m or more safety margin), truck staging space to wait when berths are full, parking lots for private cars and bicycles for hundreds of commuting employees, and the green space ratio (obligation to plant a certain percentage of the site) stipulated by ordinances such as the Factory Location Act.
📌 Mandatory Considerations in On-site Design (Items Outside Tera Calculation)
The following "living operational spaces of the site", which cannot be completed by the figures of area calculation software alone, must also be kept in mind when drawing the layout plan.
・Placement for balers compressing waste cardboard generated in massive quantities daily, temporary waste placement areas, and pallet washing stations to remove mud and dirt.
・Properly placed toilets and washrooms readily available for warehouse workers, and evacuation guidance aisles to prevent contact accidents between forklifts and pedestrians (complete separation of pedestrians and vehicles).
・Dedicated storage space for statutory slips and past ledgers that have a storage obligation for several years.
・Coordination of noise and exhaust gas considerations for neighboring residents, crime prevention and security (gate guardhouse), building height restrictions under the Civil Aeronautics Act, and access conditions such as exiting with a left turn onto arterial roads.