Treat a preset as the beginning of an equipment record
A booking team calculated eleven Euro positions using the twenty-foot dry preset. The delivered equipment record shows slightly different inside dimensions and a different door height. The earlier calculation is not automatically wrong, but its evidence applies to its original rectangle and assumptions. Update the equipment record and rerun the affected checks before using it for the shipment. A preset supports early planning; it is not a measurement or commitment concerning the unit that has been assigned.
Keep three categories distinct: the site’s historical preset, a carrier’s representative fleet example and the accepted assigned-equipment specification or measurement. Their differences may be small enough to leave the floor count unchanged, yet important enough to alter door entry or a tight row. Select one complete record for each scenario rather than mixing dimensions from multiple sources. The final file should show why the selected values describe the equipment and cargo being planned.
Compare the current twenty-foot example with the historical preset
The site’s dry twenty-foot preset uses 5898 × 2352 × 2393 mm inside and a 2340 × 2280 mm door. Hapag-Lloyd’s current Standard example table lists 5900 × 2352 × 2395 mm inside and a 2340 × 2292 mm door. The current example is two millimetres longer and taller inside, with a twelve-millimetre higher door. Those differences do not establish that a particular container has either record. They identify the assumptions that must be checked when reproducing an older calculation.
For a 2282 mm load, the historical door comparison is 2280 − 2282 = −2 mm, while the current example comparison is 2292 − 2282 = 10 mm. One screen fails and the other has a positive dimensional residual. Neither is a handling approval. The actual opening, complete loaded height and loading method must be established. This is a useful example of how a floor result can remain familiar while another part of the shipment decision changes.
| Record | Inside dimensions | Door dimensions | Status |
|---|---|---|---|
| Historical 20ft dry preset | 5898 × 2352 × 2393 mm | 2340 × 2280 mm | Site planning default |
| Hapag-Lloyd current 20ft example | 5900 × 2352 × 2395 mm | 2340 × 2292 mm | Representative fleet example |
| Hapag-Lloyd current High Cube table | 12032 × 2350 × 2700 mm | 2340 × 2597 mm | Width differs from page diagram |
| Assigned unit | Enter accepted specification | Enter accepted opening | Equipment-specific record required |
Preserve unit precision at tight thresholds
One inch is exactly 25.4 mm. A 48 × 40 inch footprint is therefore 1219.2 × 1016 mm, rather than 1200 × 1000 mm. That rounded metric substitute describes a smaller rectangle. For a 630 inch trailer floor, the corresponding length is 16002 mm, not the nominal exterior 53-foot length of 16154.4 mm. Record whether a dimension is interior, exterior or an opening before converting it. Correct units cannot fix a dimension taken from the wrong part of the equipment.
Preserve decimals through the fit calculation, while acknowledging the measurement precision of the source. Rounding a 98.5 inch inside width to 99 inches adds a fictitious 12.7 mm. That can matter when comparing two 48 inch footprints with spacing and side bands. A displayed rounded summary should not replace the saved input values. If the specification arrives in inches and the tool uses millimetres, retain both the original figure and the exact conversion in the equipment record.
Use sensitivity checks to reveal a critical dimension
For two 1165 mm square loads, a 2352 mm floor leaves 22 mm across their combined 2330 mm width. A 2350 mm floor leaves 20 mm. An illustrative 10 mm band at each wall consumes the full residual in the latter scenario. Adding any positive gap makes that pair fail at 2350 mm. This sensitivity check explains why a two-millimetre source discrepancy can matter for a tight arrangement without claiming that ten millimetres is an appropriate operating allowance.
Hapag-Lloyd’s current High Cube page has exactly such a width discrepancy: 2352 mm in the illustrated dimensions and 2350 mm in the table. Keep both values identified if testing sensitivity, then ask for the accepted assigned-unit width. Do not choose the larger figure simply because it preserves a desired count. When the source is internally inconsistent, the result should carry that uncertainty until equipment-specific information resolves it. The count alone cannot determine which source value is correct.
Update the complete scenario rather than one favorable field
When changing from dry to reefer, replace the equipment record rather than editing only height. Refrigeration machinery and insulation affect floor dimensions as well, and loading-line instructions may define another cargo envelope. When changing from Standard to pallet-wide, use the specific floor and door for that equipment family. A hybrid record with dry length, reefer height and pallet-wide width has no defensible equipment identity. It may produce a geometric result, but it does not describe a carrier example or an assigned container.
At the same time, remeasure the finished pallet envelope if packaging has changed. The floor engine does not infer wrap, corner boards, bulges or overhang from the pallet standard. A 1200 × 800 mm deck can carry a larger rectangular load. Equipment dimensions and cargo dimensions are equally important inputs. Keep their sources separate so a later reviewer can identify whether a count changed because of a new container, revised packaging or an altered spacing requirement.
Replace a preset with an assigned-unit scenario
Save the original preset result and its input values first. Enter the accepted inside length and width for the assigned unit, actual completed footprint, rotation permissions, gap and wall clearance. Save the new count, coordinates and status. Separately update the door, accepted cargo height, mass limits and loading-method record. Write the reason for each changed field and the source or measurement date.
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.
Understand what changes to proof status mean
The site’s finite search combines strip enumeration and MaxRects heuristics for identical rectangles. Some historical zero-gap container and pallet pairs have verified fixtures; custom dimensions are not automatically covered by those fixtures. If a small edit changes the label from optimal to best found while leaving the quantity unchanged, the geometric candidate may still be valid, but the proof scope has changed. Retain that distinction rather than copying the old optimal label into the revised scenario.
An area upper bound is another way the engine can establish a supported result, but a loose bound is not a packing plan. The returned final positions show one feasible arrangement under the modeled constraints. Best found does not claim mathematical maximality. Nor does any geometric status establish entry access, payload, floor bearing, thermal performance or securing. Equipment-specific documentation improves the relevance of the model, while those separate operational checks remain necessary for the actual loading proposal.
Keep a useful record through handover
Store the tool address or page name, input units, full numeric dimensions, source references and date alongside the equipment identifier when available. Include the cargo list, loaded heights and masses, spacing requirement source and the proposed handling sequence. A screenshot of a count is insufficient because two different rectangles can produce the same quantity. The saved numbers allow another planner to reproduce the candidate and identify which assumptions changed after the booking or packaging revision.
If the assigned unit is replaced, repeat the comparison rather than assuming another unit of the same nominal class is interchangeable. A source’s representative example is useful context, especially when reviewing broad equipment options, but the accepted record controls the final dimensional proposal. This approach makes the calculation auditable without pretending that a site preset guarantees equipment availability or turning a dimensional residual into an invented safety margin.
Primary sources and scope
Hapag-Lloyd twenty-foot Standard: Current fleet example and its variation notice.
Hapag-Lloyd High Cube: Current table and diagram width discrepancy.
CMA CGM container specifications: Technical examples are non-contractual and span distinct equipment families.
NIST length reference: The exact international inch conversion used in the input-record examples.