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How to Measure Your Box

Getting your box dimensions right is the first step to a perfect fit. This guide shows you how to measure correctly so your packaging fits your product, protects it during shipping, and looks great on the shelf.

The Three Dimensions

Every box is defined by three measurements: Length, Width, and Height. These are always measured from the inside of the box, not the outside.

Length (L) is the longest side of the opening. Width (W) is the shorter side of the opening. Height (H) is the distance from the bottom of the box to the top (also called depth).

The most common mistake is measuring from the outside of the box. Material thickness adds 1–3mm per side, which means an outside measurement can be 2–6mm larger than the actual interior space.

Standard Format

How to Write Your Dimensions

Always provide your dimensions in this order: Length × Width × Height (L × W × H). For example, a box that is 150mm long, 100mm wide, and 50mm tall would be written as 150 × 100 × 50mm.

Step by Step

How to Measure Your Product

Follow these four steps to get accurate dimensions for your custom box.

Measure your product

Place your product on a flat surface. Measure the length, width, and height of the product at its widest points using a ruler or callipers. Record in millimetres.

Add clearance

Add 2–3mm of clearance to each dimension. This allows the product to slide in and out of the box easily without being too loose. For fragile items, add extra room for padding.

Account for inserts

If you plan to include tissue paper, foam inserts, printed cards, or other materials inside the box, add their thickness to your dimensions. A foam insert can add 5–10mm per side.

Test with a mock-up

Before committing to a full production run, request a structural sample or mock-up. This lets you test the fit with your actual product and make adjustments before printing begins.

Pro Tips

Things to Keep in Mind

Always measure from the inside

Box dimensions refer to the interior space — not the outside of the box. The inside measurements determine whether your product fits. The outside dimensions will be slightly larger depending on material thickness.

Place your product first

Put your product on a flat surface. Measure the product itself, then add 2–3mm of clearance on each side. A box that's too tight makes it hard to insert the product. A box that's too loose lets the product shift and get damaged.

Account for inserts and padding

If your product needs tissue paper, foam inserts, or a printed card inside the box, add the thickness of those materials to your dimensions. Inserts can add 3–10mm to each dimension depending on the type.

Consider the closure

Tuck-end boxes need extra height clearance for the tuck flap to fold in. If your product fills the box right to the top, the flap may not close properly. Leave at least 5mm of headroom above the product for tuck-end styles.

Measure in millimetres

The packaging industry in Canada works in millimetres (mm). If you measure in inches, we can convert for you — but mm is more precise and avoids rounding errors. When in doubt, send us both.

Send us the product