Ordering the wrong box is an expensive habit. Too big and you're paying to ship air and buying extra void fill; too small and product gets crammed, crushed or won't fit at all. This guide explains how cardboard box sizes work, the main carton types, how to measure so your box fits the first time, and how to pick the right box for moving, shipping or storage.
Start with the job the box has to do
Before sizes and grades, be clear on how the box will be handled — the demands are different:
- Moving — boxes get stacked, carried and dropped. Single wall is fine for books and kitchenware; heavier loads want double wall.
- Shipping — cartons pass through courier networks where they're sorted and stacked under other freight, so strength and a snug fit matter.
- Storage — boxes sit under load for months, so consistent stacking strength and a tidy close-up count.
How box sizes are measured
Cartons are always listed as Length × Width × Height (L × W × H), and — this is the key point — the figures are the internal dimensions. Length and width are the two sides of the opening (length is the longer one), and height is the distance from the base to the top flaps. Always size to your product's internal fit, not the outside of the box.
To measure your product, take its longest side, its shorter side, and its height, then add a little clearance (around 5–10 mm per dimension) so it slides in without forcing. If you're using protective packaging around it, add that too.
Single wall vs double wall
The "wall" is the corrugated fluting that gives a box its strength:
- Single wall — one layer of fluting. Ideal for most everyday e-commerce, retail and light-to-medium goods up to around 15–20 kg.
- Double wall — two layers of fluting for heavier, denser or fragile items, or anything being stacked on a pallet or freighted long distances.
If a box will be stacked, travelling by freight, or carrying weight, step up to double wall — the small extra cost is far cheaper than damaged stock.
The main carton types
- Stock cartons (RSC) — the classic regular slotted carton where all flaps meet in the middle. The most economical, most versatile box for general shipping and storage. Browse Stock Cartons.
- Die-cut boxes — pre-cut, often fold-flat mailer-style boxes with a tuck or crash-lock base. Fast to assemble and popular for e-commerce. See Die Cut Boxes.
- Corrugated sheets & pads — flat board for layering, dividing or wrapping. See Corrugated Cardboard.
- Postal tubes — for rolled documents, prints, textiles and anything long and thin. See Postal Tubes.
- Insulated cartons (Chilltainers) — for chilled or perishable goods that need to stay cold in transit. See Chilltainers.
You can see the whole range together in Boxes & Cartons.
Stock carton sizes at a glance
Our Kraft stock cartons run from #1 to #10, so there's a standard size close to most products:
- Small (#1–#3, roughly 250 × 250 × 200 to 303 × 303 × 250 mm) — books, tinned goods and tools; heavier items go in smaller cartons so they stay liftable.
- Medium (#4–#7, up to around 455 × 305 × 305 mm) — the workhorse size for general packing, kitchenware and everyday e-commerce orders.
- Large (#8–#10, up to around 510 × 380 × 585 mm) — bulkier but lighter loads and larger shipments that still need to stack neatly.
How many boxes will a move need?
People almost always underestimate. As a rough starting point: a one-bedroom flat needs around 15–25 boxes, a two to three-bedroom house 40–60, and four-plus bedrooms 60–90 or more. Weight the mix toward small and medium sizes — that's where the heavy items go — and keep a few spare rather than running short mid-pack.
Right-sizing saves money
The best box is the smallest one your product safely fits in. Right-sizing cuts three costs at once: less void fill to buy, lower dimensional shipping weight, and fewer damages from product moving around. If your items don't match a standard size well, it's usually cheaper long-term to standardise on one or two carton sizes than to run a dozen odd ones.
Where a box will have empty space, pair it with the right protective packaging — void fill and protection or bubble wrap — rather than a bigger box.
How to choose
Measure your product's internal fit and add 5–10 mm clearance; pick single wall for everyday goods and double wall for heavy, fragile or freighted stock; then choose the carton type that suits how it's packed and presented. Standardising on a couple of sizes keeps ordering simple and pricing sharp. Trade accounts get tiered pricing, and for custom-printed or made-to-order cartons in your exact size, email sales@nzpackaging.nz with dimensions and quantities.
Frequently asked questions
Are box dimensions internal or external?
Internal. Size to your product's fit; the outside of the box is slightly larger once you account
for board thickness.
When do I need double wall instead of single wall?
For heavier or denser items, fragile goods, anything stacked on a pallet, or long-distance freight.
Single wall is fine for most light-to-medium shipments.
How many moving boxes do I need for a 3-bedroom house?
Plan on roughly 40–60 cartons weighted toward small and medium sizes, since that's where the
heavier items go.
Can I get boxes in a custom size or printed?
Yes — for made-to-order sizes and custom print, contact sales@nzpackaging.nz with
your dimensions, quantity and any branding.
