Why do twelve cartons fit in a drawing, yet the last one jams during packing? Start by checking what each dimension describes. The drawing may show nominal carton dimensions, while production presents filled cartons near their permitted maximum size and cases near their permitted minimum interior size. The missing space may be the clearance needed to insert the cartons, rather than space occupied by the cartons themselves.
For case fit, compare the maximum declared packing envelope of the contents, plus explicitly assigned clearances, with the minimum usable case interior. For pallet fit, pass forward the finished case outside dimensions. Keep those two checks separate.
Give each dimension a specific job
The product envelope is the bounding space occupied by the product in its packing orientation, including protrusions such as a locked pump. It informs carton design. Once that product is inside an assembled, filled and closed carton, the carton’s outside dimensions, or OD, become the physical input to case planning. Product dimensions and carton inside dimensions cannot substitute for that assembled OD. The distinction between the materials themselves is covered in carton materials versus corrugated materials.
A declared packing envelope is the per-item space entered into the arrangement calculation. State whether it is the carton’s maximum physical OD or includes additional wrap or reserved space. Arrangement space then combines those envelopes with the gaps between them. Wall clearances and headspace extend that arrangement into the required usable case inside dimensions, or ID. Usable means unobstructed space remaining after accounting for the construction, closures and any inserts.
Axis names also need a shared reference. For flap-type cases, FEFCO Recommendation No. 101, July 2006 defines length along the longer opening dimension, breadth along the shorter one, and height from opening to base. Follow the style drawing where its axis convention differs. In this article, width means breadth. Mark those directions on the drawing rather than sorting every package’s three dimensions from largest to smallest. Turning a carton on its side changes which dimension consumes case height; rotating it within an upright layer changes only its footprint.
Separate manufacturing variation from working space
Nominal dimensions identify the intended size. Tolerances define the permitted variation around it, whether symmetric or asymmetric. Maximum and minimum dimensions are the relevant specification limits for a worst-case fit check. The largest item in a small sample is an observed maximum, not proof of the largest item the specification permits.
Packing allowance is intentionally reserved space for the packing operation. Give it a location and purpose: gaps occur between items, wall clearance occurs between the arrangement and the case, and headspace lies above the contents. Bottom pads and layer separators occupy material space of their own. An empty gap budget does not hold cartons apart during transport; maintained separation requires a suitable physical arrangement or restraint.
Keep a single allowance ledger. If the declared packing envelope already contains a handling reserve, do not add that same reserve again without a separate purpose. Likewise, once carton dimensions include their positive tolerance, adding it again enlarges the case unnecessarily. Conversely, a layout with no working allowance assumes that insertion and closure need no additional room. That assumption needs evidence from the intended packing process, not a universal clearance rule.
Build the case interior one axis at a time
Consider a hypothetical P-100 lotion bottle in an upright retail carton. Dimension triples below are length × width × height, in millimetres. All dimensions, tolerances, clearances and supplier confirmations in this example are illustrative assumptions, not measurements or recommended industry values. The bottle’s maximum product envelope is 92 × 52 × 140 mm. Its filled, closed carton has nominal OD of 100 × 60 × 150 mm, with assumed tolerances of ±1 mm in length and width and ±2 mm in height.
The maximum carton OD is therefore 101 × 61 × 152 mm. These limits include seams and permitted bulge in the agreed measurement condition. No extra wrap or per-item handling reserve is included, so the declared packing envelope equals that maximum OD.
Arrange four cartons along case length, three along width and one high: 4 × 3 × 1 = 12 cartons. Each carton’s 101 mm dimension runs along case length; its 152 mm dimension remains vertical. Allow 2 mm between adjacent cartons, 3 mm at each opposing side wall and end wall, and 8 mm above the tallest carton. The cartons rest on the closed base, with no additional bottom reserve, pads or partitions.
Four cartons create three lengthwise gaps; three cartons create two widthwise gaps. Before wall clearance and headspace, the arrangement occupies 410 × 187 × 152 mm. Adding the assigned clearances gives:
- Required length: 4 × 101 + 3 × 2 + 2 × 3 = 416 mm.
- Required width: 3 × 61 + 2 × 2 + 2 × 3 = 193 mm.
- Required height: 1 × 152 + 8 = 160 mm.
The result is 416 × 193 × 160 mm minimum usable case ID. Height runs from the supporting base surface to the lowest relevant obstruction under the closed top. A flap or insert cannot occupy the same space as the declared headspace.
Longitudinal section through one row. All dimensions are in millimeters; gaps and end clearances are enlarged for clarity.
The schedule below preserves the distinct values through the supplier and pallet decisions that follow. For a live specification, replace assumed inputs with traceable measurements or agreed limits and record the drawing revision and measurement condition.
| Dimension | L × W × H (mm) | Basis | Downstream use |
|---|---|---|---|
| Product envelope, maximum | 92 × 52 × 140 | Assumed | Carton design |
| Assembled carton OD, nominal | 100 × 60 × 150 | Assumed | Carton specification |
| Assembled carton OD, maximum | 101 × 61 × 152 | Calculated from assumed tolerances | Physical fit limit |
| Declared packing envelope | 101 × 61 × 152 | Assumed equal to maximum OD | Arrangement input |
| Arrangement space, including gaps | 410 × 187 × 152 | Calculated | Add wall clearance and headspace |
| Usable case ID, required minimum | 416 × 193 × 160 | Calculated | Supplier acceptance limit |
| Usable case ID, nominal target | 418 × 195 × 162 | Assumed supplier target | Manufacture with ±2 mm limits |
| Finished case OD, maximum | 428 × 205 × 178 | Assumed supplier-confirmed limit | Pallet footprint check |
Scroll to compare all columns.
Case Builder separates carton OD, between-carton gaps and clearance around the bundle. Check the field meanings before entering allowances: its top-and-bottom setting applies at both opposing surfaces. The example assigns 8 mm above and zero below, so preserve that asymmetric requirement explicitly rather than entering 8 mm as a paired clearance.
Check the smallest permitted case, not just the nominal drawing
Suppose an available case has nominal usable ID of 414 × 192 × 160 mm, each dimension permitted to vary by ±2 mm. Using nominal cartons with the same clearances gives a requirement of 412 × 190 × 158 mm. The drawing appears to have 2 mm to spare on every axis.
The comparison changes when both specifications reach their adverse limits. The table shows the required space against available case space; the margin is available minus required.
| Axis | Nominal required / available (mm) | Worst-case required / available (mm) | Margin: nominal / worst (mm) |
|---|---|---|---|
| Length | 412 / 414 | 416 / 412 | +2 / −4 |
| Width | 190 / 192 | 193 / 190 | +2 / −3 |
| Height | 158 / 160 | 160 / 158 | +2 / −2 |
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The candidate fails the specified working-space budget on every axis. That does not prove the solid cartons cannot be squeezed inside: the deficits include lost clearances. It does show that the fit cannot be approved against the stated requirements. This is a deterministic limit check, not a prediction of how often the extremes will occur.
To retain the required minimum under the assumed ±2 mm case tolerance, the usable-ID nominal target becomes 418 × 195 × 162 mm. Specifying 416 × 193 × 160 mm merely as nominal would permit undersized interiors. Conversely, adding the carton’s 1 mm positive length tolerance again after using its 101 mm maximum would unnecessarily add another 4 mm to the four-carton row.
Use finished outside dimensions for the pallet decision
Use the 418 × 195 × 162 mm nominal ID target in Shipper Builder for preliminary physical shipper planning. Retain 416 × 193 × 160 mm as the minimum usable-space requirement in the supplier specification; do not add the packing clearances again. The converter still needs to establish the actual construction and its dimensional limits.
Do not universally convert ID to OD by adding twice the nominal board caliper. FEFCO Recommendation No. 101 explains that creasing allowances depend on factors including material grade, flute form and case style. Scores, folds, joints and closure geometry belong in the converter’s construction-specific assessment. A planning estimate cannot establish the maximum loaded, sealed outside envelope.
For the revised case, suppose the converter confirms maximum finished OD of 428 × 205 × 178 mm, including dimensional variation and allowed bulge under the agreed filled-and-closed condition. On an assumed available pallet footprint of 1200 × 1000 mm, rotate the cases within the horizontal plane: five 205 mm widths occupy 1025 mm, and two 428 mm lengths occupy 856 mm. That uniform grid holds ten cases per layer without overhang, assuming no additional inter-case spacing.
Using the required case ID instead would falsely suggest six across: 6 × 193 = 1158 mm. Their actual maximum outside widths total 6 × 205 = 1230 mm, exceeding the pallet by 30 mm. Ten cases is the result for this grid, not a claimed optimum. Height, mass, strength and stability remain separate checks in the carton-to-pallet workflow.
Confirm the fit on assembled packs
Agree on the inspection method with the converter. FEFCO Recommendation No. 101 determines internal dimensions from crease-centre measurements on a flattened case, with applicable adjustments; its scope primarily concerns style 0201 flap-type cases. That dimensional method should not be confused with an assembled trial demonstrating usable clearance and successful loading.
For that trial, record the material condition, temperature and humidity, conditioning duration, assembly and closure method, and measuring equipment. Measure filled cartons across bulges and seams without squeezing them into compliance. Check case squareness and the narrowest relevant clear spans, including the loading opening and insertion path, rather than measuring only its unobstructed middle. Check height above the closed base and beneath the closed top; measure finished OD after loading and sealing.
Include cartons near their upper dimensional limits and cases near their lower limits, using representative production samples. Test the intended loading sequence, equipment and operating conditions, with acceptance criteria for insertion, carton damage and closure agreed beforehand. Also examine smaller cartons in larger cases for excessive movement. A gentle hand fit does not establish automated-line performance.
Release the specification with the measured results, dimensional limits and allowance locations attached. When the carton, case construction or closure changes, repeat the affected fit check before carrying its dimensions into the next packaging level.