In modern logistics facility planning, layout design relying on experience and intuition is no longer viable. A distribution center's center sizing calculation is a complex set of additions and subtractions repeating the movement and storage of cases and loose items, which must be solved using mathematical models.
Throughout the calculation process, depending on the objective (which area is being designed), base units shift sequentially: from issue frequency, loose pieces, case conversion, pallet (PL) conversion, volume conversion, to weight conversion. In TCalc 2, individual calculation logics for each site are integrated. By taking the overall average value (Tera setting) as the starting point, it theoretically calculates inventory and inbound volumes to logically determine the optimal sequence of scale—from inbound through shipping space area and berth count, shipping work space, and storage space, down to final building area and site area.
In data processing for center sizing calculation, TCalc 2 focuses particularly on pallet storage efficiency in storage space, actively using "PL conversion (pallet converted value)" as the key indicator for rank configuration.
💡 Two Critical Reasons to Use "Overall Average" in Shipping Data
1. Complete Prevention of Omitted Calculations: If analysis is conducted by selecting only specific shipping days (e.g., peak days at the end of the month), items with no shipping history on that day (such as long-tail items) will be completely left out of the calculation. Using the overall average accurately covers the required storage space for all items.
2. Prevention of Over-Investment (Over-specification): Calculating center scale using peak days results in oversized buildings and equipment, leading to continuous waste in depreciation costs. As a fundamental principle of logistics, peak surplus volume should be addressed through operational strategies—such as leveraging safety stock or advancing outbound schedules. Hardware scale must be aligned with "stable average operations."
Based on this philosophy, TCalc 2 strictly separates flow lines for case shipments and piece shipments. By storing and expanding up to 32 aggregate tables (including converted values) within the internal Access system, it enables multi-faceted and flexible verification simulations.
The most common trap in logistics facility planning is relying directly on current inventory data (actual WMS values) for area calculation. Because actual figures contain unnecessary idle inventory and stockouts, it is crucial to theoretically calculate inventory and inbound volumes from accurate shipping data and cross-verify them against current actuals.
Based on required inventory per item (PL conversion) calculated from shipping data, the system automatically determines pallet loading styles. By finely distinguishing single-item full pallets ("Dedicated PL") from mixed pallets accommodating multiple small-lot items ("2 to 8 Mixed PLs"), it calculates an extremely precise required pallet count reflecting actual site conditions, directly translating to storage space area.
When conducting theoretical calculations for inventory and inbound volumes, how inbound timing is set drastically changes the required footprint. By simulating intentional staggering of inbound dates per item according to fluctuating inventory days (e.g., ordering cycles of 6 days), the peak total inventory volume across the distribution center can be suppressed, ultimately minimizing the required building area.
Furthermore, the optimal unit handling format is automatically determined from inbound volume per item (e.g., full pallet units for ≥0.5 PL, or piece/foldable container units for ≤0.5 cases), accurately estimating total inbound volume unloaded from trucks.
Unlike outbound operations, inbound operations are relatively easy to control on the company side (e.g., specifying and staggering delivery dates/times). Scheduling inbound activity to share idle time slots for shipping space area and berth count significantly reduces dedicated inbound space, directly contributing to cost reduction.
Securing adequate shipping space area and berth count is the final line of defense to prevent delivery delays. This vital space accommodates staging and holding for case goods retrieved from storage space as well as picked/assorted loose items consolidated by destination, holding them post-inspection and packing until loaded onto trucks.
Shipping work space houses the highest concentration of personnel in the center and serves as the operational core directly impacting productivity. Destination sorting areas for cases, picking racks for loose items (flow racks, medium-duty shelving), and packing line areas are calculated with precision.
This calculates the reserve area (storage space) required to store bulk inventory remaining after subtracting stock already allocated to active shipping work space (flow racks and medium-duty shelves) from total center inventory.
⚠️ 5m Threshold & Fire Service Act "Virtual Floor" Rule
If the bottom level of items stored on the top pallet rack beam exceeds 5,000mm (5m) in height, Building Standards and Fire Service laws classify it as containing a "virtual floor." This triggers mandatory installation of additional fire sprinklers and strict firewalls, requiring extreme caution when setting rack heights.
To finalize total facility footprint, essential auxiliary areas are added to the net operational footprint calculated above (inbound/shipping space area and berth count, shipping work space, and storage space).
Specifically, this includes office space for center managers and administrative staff, welfare areas such as breakrooms and locker rooms, storage for consumables/packaging materials (unfolded cartons, tape, dunnage, forms), and main arterial aisles (e.g., 4m wide) allowing safe two-way forklift traffic. Additionally, overlapping areas shared between inbound and outbound operations at different time windows are deducted, yielding a precise, non-wasteful gross floor area.
Once required internal floor space is finalized, calculations move to physical building hardware and land requirements.
Simulations are performed for the building area housing the logistics center. Optimal building volume is decided based on land constraints and investment budgets.
Final site area requires far more space than simply fitting the building footprint. Expansive external spaces are mandatory for trucks to maneuver safely and smoothly while maintaining harmony with surrounding environments.
In addition to top-down building footprint area, the required site area must include turning lanes allowing large 16m trailers to dock without shunting (vehicle width + ≥1m safety margin), truck staging areas for peak queues, parking/bicycle lots for hundreds of commuting employees, and mandatory greenbelt ratios set by local ordinances (e.g., Factory Location Law requirements).
📌 Essential Operational Considerations (Non-TCalc Factors)
Calculations from software alone are insufficient; the following real-world operational spaces must always be kept in mind when drafting physical layouts:
• Space for corrugated cardboard balers, temporary waste storage, and pallet washing areas to clean off mud and debris.
• Appropriately distributed restrooms and washrooms for floor workers, and clear evacuation routes with complete pedestrian-vehicle separation to prevent forklift accidents.
• Dedicated storage rooms for statutory forms and historical records subject to multi-year retention laws.
• Environmental adjustments for noise/exhaust mitigation for neighbors, security checkpoints (guardhouses), building height restrictions under aviation laws, and traffic access constraints such as left-turn-only exits onto main arteries.