Case size planner

What the calculator does

The case size planner sizes a rectangular RSC (regular slotted container) for a product packed in a simple grid. It multiplies each product dimension plus per-unit clearance by the number of units in that direction, then adds board thickness to estimate the outside of the box. It is a planning model, not a substitute for a converter drawing or a physical pack test.

• Units per case: the product of units along length, units along width and layers.
• Internal length and width: the two side dimensions of the interior envelope, longer value reported as length.
• Internal height is the layer count multiplied by the sum of product height and per-unit clearance.
• Estimated external size: internal side dimensions plus two board thicknesses and internal height plus four board thicknesses, rounded to at most three decimal places.

Entering the product and arrangement

Start with one unit's length, width and height in inches. Then describe the arrangement: units along the length direction, units along the width direction, and layers stacked vertically. Each count must be a whole number of at least one.

Clearance is the total extra space added to each product cell along each axis, not a gap added separately on both sides. The example starts at 0.125 in. Set it to zero only if the product needs no placement room, because the model applies it uniformly and cannot represent one-sided looseness.

How the internal envelope is computed

The first side span is units along length multiplied by (product length + clearance). The second is units along width multiplied by (product width + clearance). Interior height is layers multiplied by (product height + clearance). Because clearance is added per unit, a larger count in any direction grows that dimension faster than product size alone.

The calculator sorts the two side dimensions longest-first before reporting. Whichever computed value is larger is shown as internal length, the smaller as internal width. The reported length may not match the direction you called length if the width span comes out longer. Height is never swapped with a side dimension.

How the external estimate is built

The estimated external size adds two board thicknesses, called caliper, across each side dimension and four across the height, the closing-flap direction. This reflects two walls meeting on each side and stacked flaps top and bottom. Caliper is entered in inches and defaults to 0.125 in.

External side dimensions follow the same longest-first ordering as the internal ones, so the larger side plus two calipers is listed first. External height is internal height plus four calipers. The result is an estimate: real manufacturing allowances, score-line take-up and board variation are not modeled.

Worked example: default starting scenario

Take a 12 by 10 by 8 in product packed 4 along the length, 3 along the width, single layer, with 0.125 in clearance and 0.125 in board thickness. Interior length is 4 times 12.125, or 48.5 in. Interior width is 3 times 10.125, or 30.375 in. Interior height is 8.125 in. Units per case is 12.

The external estimate adds 0.25 in to each side and 0.5 in to the height, giving 48.75 by 30.625 by 8.625 in. Since 48.5 exceeds 30.375, the length direction stays first, matching the input orientation here.

Worked example: smaller product, two layers

Now take a 3 by 3 by 6 in product in a 4 by 3 by 2 arrangement with the same clearance and caliper. Interior length is 4 times 3.125, or 12.5 in. Interior width is 3 times 3.125, or 9.375 in. Interior height is 2 times 6.125, or 12.25 in. Units per case is 24.

The external estimate is 12.75 by 9.625 by 12.75 in. External height equals external length here, because 12.25 plus 0.5 in of flap caliper matches 12.5 plus 0.25 in of side caliper. For this smaller product, moving from one to two layers changes height and unit count while keeping the footprint fixed. Check the height constraint before adding layers.

Reading changes and edge cases

Each input affects output predictably. Increasing a count lengthens that arrangement axis before the two side dimensions are sorted, and also increases units per case. Increasing clearance grows every dimension in proportion to the counts, so clearance on a densely packed case adds up quickly. Increasing caliper adds exactly two calipers to each side and four to the height.

A useful edge case is a tall, narrow arrangement. Pack few units along the sides but stack many layers and the computed height can exceed both side spans. The report still lists side dimensions longest-first and keeps height separate, so a 12.25 in height with 12.5 and 9.375 in sides reads naturally, but a 20 in height with 12 in sides will look tall. The model does not warn about unstable proportions; you must judge whether a tall case needs a different arrangement.

Limits of the model

This is a rectangular RSC planning model assuming a plain box with no interior features. Partitions, inserts, tolerances and fragile-product protection require a converter drawing and a physical pack before committing to production. Clearance is a uniform planning allowance, not a measured tolerance, and the caliper addition is a geometric estimate, not a manufacturing specification.

• No partitions, inserts or padding are modeled.
• Every unit is assumed to sit the same way.
• No tolerance, compression or fragile-product checks.
• External size is a screening estimate, not a die line.

Questions about case size planner