How to Choose the Right
Corrugated Box Size
Getting the size right saves money twice: less wasted void fill, and lower dimensional weight charges. This guide covers how boxes are measured, what the board ratings mean, and which of our four size ranges fits your product.
Length × Width × Depth, Inside Dimensions
Corrugated boxes are always specified by inside dimensions, because that is the space your product actually occupies. Outside dimensions differ by the board thickness.
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Length is the longest opening edge
Look down into the open box. The longer of the two edges of the opening is the length.
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Width is the shorter opening edge
The remaining edge of the opening. Length and width together describe the footprint.
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Depth is top to bottom
Measured from the opening down to the inside base. Depth is what most people get wrong when ordering.
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Add clearance for protection
Allow roughly 1″ to 2″ on each dimension for cushioning if the contents are fragile. For books, apparel or non-fragile goods, a snug fit is better and cheaper to ship.
Four Size Ranges, 300+ Stock Sizes
We group our 32 ECT Kraft boxes by length. Every range ships flat and carries volume pricing that improves with quantity.
6″ to 11″
Compact items: cosmetics, small electronics, jewellery, samples, spare parts, subscription boxes.
Shop small 98 sizes12″ to 15″
The e-commerce workhorse: apparel, books, kitchenware, packaged food, most everyday parcels.
Shop standard 100 sizes16″ to 20″
Bulkier goods: small appliances, multi-item orders, retail case packs, moving cartons.
Shop large 58 sizes21″ to 36″
Long or oversized: artwork, lampshades, sporting goods, furniture parts, wardrobe cartons.
Shop oversizedWhat 32 ECT and C-Flute Actually Mean
ECT: edge crush test
ECT measures how much force the board withstands on its edge before crushing, in pounds per inch. Higher means more stacking strength.
| Grade | Typical use |
|---|---|
| 29 ECT | Light contents, minimal stacking |
| 32 ECT | General shipping and storage — our standard |
| 40 ECT | Heavier goods, taller stacks |
| 44 ECT | Heavy or long-transit freight |
Almost all of our stock is 32 ECT, which handles the overwhelming majority of parcel and warehouse work. Heavier grades are available to order.
Flute: the wave between the liners
Corrugated board is two flat liners with a fluted wave glued between them. The flute profile decides the balance between cushioning and printability.
| Flute | Character |
|---|---|
| B | Thinner, flatter, better for print and die-cutting |
| C | Medium profile — best all-round strength and stackability |
Our standard is C-flute single wall. It is the most widely used profile in North America and the reason "32C Kraft" is shorthand for a general-purpose shipping box.
Kraft simply refers to the unbleached brown paper. It is fully recyclable and takes labels, stamps and print cleanly.
Sizing Questions We Get Asked
Are box dimensions inside or outside measurements?
Inside. Corrugated boxes are specified by internal dimensions because that is the usable space. Outside dimensions are larger by roughly the board thickness on each side — about 1/8″ per wall for single-wall C-flute.
How much clearance should I leave around my product?
For fragile goods, allow 1″ to 2″ on each dimension so cushioning can absorb impact. For books, apparel and other non-fragile items, a snug fit is better — it reduces void fill and keeps dimensional weight down.
What is dimensional weight and why does box size affect shipping cost?
Carriers bill on whichever is greater: actual weight, or dimensional weight calculated from the parcel's volume. An oversized box on a light product means you pay for air. Choosing a box that fits closely is often the cheapest single change you can make to your shipping costs.
Do I need a stronger board than 32 ECT?
Usually not. 32 ECT single wall handles most parcel shipping and warehouse stacking. Consider 40 or 44 ECT if the contents are heavy, the boxes will be stacked several high for long periods, or the shipment involves multiple freight handoffs.
What does "25/500" mean on your product names?
The first number is how many boxes come in a bundle, the second is how many are on a skid. So 25/500 means bundles of 25, with 500 per skid. Bundle size varies by box — some are 10, 15 or 20 — and volume pricing starts at one bundle.
What if none of your stock sizes fit?
We manufacture custom corrugated boxes to your exact inside dimensions in our Scarborough facility, including print and finish. Request a quote with your measurements and quantity.
Still not sure which box you need?
Send us your product dimensions and quantity. We manufacture in Scarborough and deliver across the GTA, so you are talking to the people who make the boxes.