Start with the refrigerated shipment requirement
A small chilled shipment produces eight Euro pallets and the booking desk asks whether a twenty-foot container is sufficient. A dry-container result is an incomplete answer. Refrigeration machinery, insulation and equipment construction change the rectangular space available, while the temperature-control plan introduces requirements that a floor drawing cannot evaluate. Establish the reefer type, finished pallet envelopes and accepted cargo loading instructions first. Use the geometry as one check within that plan rather than treating the familiar dry count as a refrigerated capacity promise.
This article uses two published carrier examples to show why selecting a reefer-specific record matters. Hapag-Lloyd’s twenty-foot reefer inside table is 5450 × 2280 × 2159 mm. CMA CGM lists a twenty-foot reefer interior of 5456 × 2294 × 2273 mm and separately publishes a cargo-usable-height figure. These are fleet examples from different specifications. They do not identify the unit that will arrive at your warehouse, and you should not combine their longest, widest and tallest values into a synthetic container.
Hand-check a simple eight-pallet floor arrangement
Take the Hapag-Lloyd example floor of 5450 × 2280 mm and identical 1200 × 800 mm footprints. With the 1200 mm side along the container, floor(5450 / 1200) = 4 and floor(2280 / 800) = 2, giving eight positions. Four rows occupy 4800 mm length, leaving 650 mm in that direction before any end spacing. Two pallets occupy 1600 mm width, leaving 680 mm before side spacing. This is a feasible simple rectangle arrangement under the stated zero-clearance assumptions, not an assertion of maximum reefer capacity.
Turning every footprint gives floor(5450 / 800) × floor(2280 / 1200) = 6 × 1 = 6. A mixed-orientation search might improve on these two grids, but any result must be reviewed with its actual input record and status. Area division gives floor((5450 × 2280) / (1200 × 800)) = 12 as a loose ceiling. It does not produce twelve placements, and it ignores the airflow and loading instructions that may reduce the usable region further.
| Equipment record | Inside length × width × height | Door width × height |
|---|---|---|
| Hapag-Lloyd reefer | 5450 × 2280 × 2159 mm | 2290 × 2264 mm |
| CMA CGM reefer | 5456 × 2294 × 2273 mm | 2290 × 2264 mm |
| Site historical dry preset | 5898 × 2352 × 2393 mm | 2340 × 2280 mm |
A large door is not the cargo height limit
The Hapag-Lloyd example lists a 2264 mm door height but a 2159 mm inside height. A 2200 mm load therefore appears short enough for that door while exceeding the stated interior by 41 mm. Comparing only the door would give the wrong dimensional screen. Check the smaller applicable envelope and any separate cargo loading line or usable-height instruction. The published figures may describe different reference planes or fleet construction, so an inconsistency is a reason to clarify the assigned specification rather than to assume extra cargo space.
For a hypothetical 2000 mm accepted total loaded-height limit, a 144 mm pallet base and 250 mm cases, floor((2000 − 144) / 250) = 7 complete layers. Those layers stand 1894 mm high. Eight would stand 2144 mm. This example assumes the 2000 mm limit has already been agreed for the cargo and equipment; it is not a reefer loading-line recommendation. Count top sheets, boards and other materials in the measured finished envelope, and examine the pallet gross weight when deciding how many layers to build.
Protect the airflow plan from the packing calculation
A floor optimizer maximizes identical rectangular placements in a two-dimensional region. It has no model of supply-air flow, return-air passages, product respiration, packaging ventilation, humidity or the refrigeration control settings. A high geometric utilization percentage does not measure cooling performance. Obtain the carrier’s applicable refrigerated-cargo instructions and product-specific handling requirements, and define which areas must remain available before trying to optimize pallet positions. This is especially important when the proposed cargo envelope covers almost the entire floor.
Do not use an arbitrary gap as a universal airflow allowance. The site’s gap input creates geometric separation between modeled footprints, while wall clearance removes a band from the rectangle. Those controls can represent a specific agreed spatial requirement, but they cannot calculate the correct airflow space for a product. An instruction to keep a loading line clear may concern height rather than a uniform side band. Translate the actual requirement into the appropriate geometric input only where the model can represent it.
Measure completed loads and keep the order arithmetic separate
For 315 cases at forty cases per full pallet, ceil(315 / 40) = 8 pallets. Seven contain forty cases and the last contains thirty-five. If the footprint stays 1200 × 800 mm, all eight occupy the same floor area despite their differing heights or weights. The engine cannot infer the last pallet’s smaller gross mass from the case order. Build a pallet list with actual case quantity, envelope and mass so transport and refrigeration reviewers can assess the shipment being sent.
Stretch wrap bulges and corner boards may make a loaded Euro pallet 1230 × 830 mm. The same simple grid then gives floor(5450 / 1230) × floor(2280 / 830) = 4 × 2 = 8, but its occupied rectangle becomes 4920 × 1660 mm. The unchanged count can conceal a different residual region. Record the measured footprint rather than preserving the nominal standard simply because the output count happens to match. Any protrusion at a different height also deserves handling review beyond the floor model.
Prepare an eight-pallet reefer record
In the full floor planner, replace the dry preset’s length and width with 5450 and 2280 mm for this worked example. Enter 1200 × 800 mm footprints, rotation enabled and zero spacing for the comparison only. Record the returned count and proof status. Then substitute the assigned reefer dimensions, actual loaded footprints and the carrier’s agreed spatial restrictions. Review cargo height and temperature-control instructions separately before using the plan.
Write your own input record beside this example: equipment identifier; dimension source and date; actual loaded footprint; rotation; gap; wall clearance; loaded height; result count and proof status. Retain the record with the layout.
Interpret custom results cautiously
The engine enumerates strip candidates and applies several finite MaxRects heuristics for one identical rectangle size. It validates final positions against its modeled boundaries and spacing. Unless a supported proof condition establishes the result, best found means the largest valid candidate discovered by those rules, not a global mathematical optimum. A custom reefer is not automatically covered by the site’s verified dry-container fixtures. Keep the status and coordinates, especially when a small dimension change alters the count.
If the actual cargo needs irregular obstructions or nonuniform reserved channels, a smaller overall rectangle may only approximate the problem. Explain that approximation in the record and obtain a separate drawing when it loses important detail. Payload, floor loading and restraint remain independent checks. The useful output of this process is an equipment-specific proposal with explicit spatial and thermal assumptions, not a single reefer pallet number detached from the shipment.
Primary sources and scope
Hapag-Lloyd twenty-foot reefer: Inside and door tables for a fleet example.
CMA CGM equipment tables: Separate reefer dimensions and cargo usable height; representative non-contractual data.
EPAL Euro pallet: Reference pallet dimensions used in the hand calculation.