How case sizing works
A shipping case is sized from the inside out: the product's footprint times how many units go in each direction, plus a little clearance so units slide in without crushing. That gives the internal dimensions a converter needs. The external dimensions — what matters for pallets and freight — add the board thickness: roughly twice the caliper on length and width, and four layers where the flaps meet on top and bottom.
Choosing the arrangement
- Keep the case liftable. More units per case cuts corrugate cost per unit, but a case a packer can't lift slows everything down.
- Aim at the pallet. A case footprint that divides evenly into 48 × 40 wastes no deck space — check yours with the pallet calculator.
- Match retail multiples. Cases of 6, 12, or 24 align with how stores order and shelve.
Once the case is sized, verify it survives the stack with the box compression calculator and estimate its freight profile with the freight class calculator.
Questions
How do you calculate case dimensions?
Multiply the product dimension by the number of units in that direction, add a small clearance per unit so product slides in, and use corrugated convention: length is the longer opening side, width the shorter, depth the height. That gives internal dimensions; add board thickness for external.
What is the difference between internal and external case dimensions?
Internal dimensions describe the space the product occupies and are what you spec to a converter. External dimensions add the board thickness and flap layers, and are what pallets, trailers, and freight calculations see.
How much clearance should a case have?
Enough that units load without force but do not rattle — commonly around an eighth of an inch per unit, more for fragile or irregular product. Too much clearance lets product shift and the case bulge.
How many units should go in a case?
Balance corrugate cost per unit against liftability and retail ordering multiples like 6, 12, or 24. Then check that the resulting footprint fills a pallet layer efficiently before locking it in.
Size the case, then price the pack.
PackOS computes case pack, pallet build, and freight as part of the quote — upload a file and the packout comes with it.