Carton Size Calculator: From Product to Outercase
Sizing a shipping carton has two traps, and both of them are easy to walk into. The first is confusing the space the product needs with the space the carton occupies. The second is forgetting that a carton is measured and folded on the outside while it holds things on the inside, so board thickness has to be added somewhere.
Carton and Board Calculator
Fill in the product and pack fields, then choose Calculate.
This calculator takes a product size and a pack count, and works forward to an inner size, an outer size with flute compensation applied, how many cartons fit a pallet, and a specification line you can paste straight into a brief.
It runs entirely in your browser. Nothing is sent anywhere, and no figure you enter leaves the page.
Carton Size Calculator: From Product to Outercase
Sizing a carton is a sequence, not a single measurement. It starts with one unit, multiplies by the pack arrangement, adds the clearance the packing method needs, and only then applies the board.
The order matters. Clearance is added to the product envelope before the board is accounted for, because clearance is space the product needs and board thickness is space the carton takes. Adding them in the wrong order produces a carton that is either loose or impossible to close.
The calculator follows that order and shows each step, so you can see where a number came from rather than accepting a total.
Inner Size vs Outer Size
Inner size is the usable cavity. Outer size is what the carton measures on the outside, and what your freight and pallet calculations have to use. For a single-wall carton the difference is small; for a double-wall carton it is not, and it compounds across a pallet load.
The calculator reports both, and states the compensation it applied so the arithmetic is visible. If you are sending dimensions to a supplier, say which of the two you are quoting — a carton specified from the wrong one is a carton that has to be remade.
A related point: the outer size is also the size the carton presents to a pallet. Two millimetres of board, multiplied across a five-by-four arrangement, is the difference between a load that fits a footprint and one that overhangs it.
Board Flute and Ply: E, B, C, BC, EB
Flute is the corrugated layer between the liners, and its height is what gives a carton its thickness and most of its stacking strength. The letter is a standard designation, and the trade-off between them is consistent: taller flute carries more load, thinner flute prints and folds more cleanly.
**E flute** is the thinnest of the common grades, and the one that behaves most like a folding carton. It suits small, light retail packs where print quality matters more than stacking strength.
**B flute** sits above it and is the general-purpose grade for small and medium shipping cartons. It is the usual answer when a buyer asks for something that protects without taking much freight volume.
**C flute** is thicker again and is the common choice for larger cartons and heavier contents. It is where a pack starts to be judged on stacking rather than on appearance.
**BC double wall** combines the two and is the grade for heavy or tall loads, or for anything that will be stacked several high in a warehouse. **EB double wall** pairs a fine outer flute with a stronger inner one, and is the compromise when a pack needs both a printable surface and real load capacity.
The table below is the compensation the calculator applies for each grade. It is a working figure for sizing, not a board specification.
| Grade | Ply | Compensation applied per side | Typical use |
|---|---|---|---|
| E flute | single wall | about 1.5 mm | small light retail packs |
| B flute | single wall | about 3 mm | general shipping cartons |
| C flute | single wall | about 4 mm | larger cartons, heavier contents |
| BC double wall | double wall | about 7 mm | heavy or tall stacked loads |
| EB double wall | double wall | about 5 mm | printable surface with load capacity |
How Many Cartons Fit a Pallet and a Container
Pallet and container counts are the fastest way to see whether a carton size is practical. A carton that is a few millimetres too wide for a clean pallet arrangement can waste a large share of the footprint, and that waste repeats on every load.
The calculator uses nominal internal dimensions for the pallet and container figures, and states them so you can substitute your carrier's own. Real capacity depends on pallet type, overhang rules, load height limits and how the cartons interlock, so treat the count as a planning figure.
If a carton count comes out low, the useful question is usually not whether a bigger carton is better, but whether the pack arrangement inside it can change. Rotating a product, or switching from a single layer to two, often recovers more footprint than resizing the carton.
What Drives Carton Cost
There is no price on this page, and this section is not a price. What it does is list the things that move a carton specification, so a brief can be written with them settled rather than discovered later.
**Board area, not just board grade.** A carton's material is bought as a flat sheet. Changing a dimension changes the sheet, and a small dimensional change can push a carton onto a different sheet layout.
**Flute and ply.** Moving up a grade adds material and weight, and weight is paid for again in freight.
**Print coverage and colour count.** Coverage and the number of colours drive the print route, and the print route drives setup.
**The number of cutting forms.** Every distinct size needs its own form. Reducing the number of sizes in a range is often the single largest lever, and it is a design decision rather than a purchasing one.
**Packing and freight profile.** How many cartons fit a pallet, and how many pallets fit a container, changes the landed cost of the same carton far more than a small board downgrade would.
**Order quantity against setup.** Setup is spread across the run. The relevant question is which parts of the specification are fixed and which scale, and that is a conversation with your supplier rather than a formula.
What This Calculator Does Not Do
The calculator does arithmetic on the numbers you give it. It does not know your product, your carrier or your warehouse, so there are things it stays out of by design.
Where a figure is an approximation, the page says so. A sizing tool that presents planning numbers as engineering results is the kind of tool that gets someone's stock damaged.
- It does not do structural engineering. Stacking strength, compression and drop performance depend on board grade, moisture, load duration and handling, and are settled by testing rather than by a form.
- It does not price anything. Cost drivers are listed; no figure, range or comparison is produced.
- It does not state a minimum order quantity or a schedule. Both are confirmed against the specification and the packing method.
- It does not replace a physical sample. A sample carton is what proves the inner size, the closure and the pallet arrangement actually work.
Structures and Pages This Tool Points To
The category page this tool sits under. /products/corrugated-shipping-boxes/
ProductsEverything in this section. /products/
Corrugated Shipping BoxesThe parent category for this calculator./products/corrugated-shipping-boxes/
Corrugated BoxesFluted board structures and their uses./products/corrugated-boxes/
Custom Shipping BoxesShippers built to your own dimensions./products/custom-shipping-boxes/
Folding CartonsWhere a lighter board is the right answer./products/folding-cartons/
Kraft BoxesUnbleached liner options for shippers./products/kraft-boxes/
Inserts and DividersInternal geometry that changes the outer size./products/inserts-dividers/
Custom BoxesMade-to-measure structures across board grades./products/custom-boxes/
Hinged Lid BoxesAttached-lid construction for repeat opening./products/hinged-lid-boxes/
Should I give my supplier inner or outer carton dimensions?
Give the inner dimensions the product needs, and say that they are inner. The supplier derives the outer size from the board grade. Stating an outer size and calling it inner is the most common sizing error.
How much clearance should I add around the product?
Enough for the packing material and for a person to load it without forcing. The calculator takes a clearance value as an input rather than assuming one, because the right number depends on whether the product is bagged, wrapped or loose.
Why did my carton count per pallet change when I only changed the flute?
Board thickness changes the outer size. On a pallet, that difference multiplies across every carton in the arrangement, so a grade change can move the count even though the product did not change.
Can one carton size serve several products?
Often, and it usually reduces the number of cutting forms in a range. The trade-off is more internal void, which needs an insert or packing material to control. The pallet and container counts on this page are the quickest way to see whether the compromise is worth it.
Send the Carton Specification On
Copy the specification line above straight into a brief, a spreadsheet or an enquiry. It carries the inner size, the outer size, the board grade you used and the pack arrangement, so whoever picks it up is working from the same numbers you are.