How to Measure a Box for Custom Packaging (L x W x H)
Updated · Vorex Packaging
To measure a box for custom packaging, measure the inside dimensions in the order length x width x height. Length is the longer side of the opening, width is the shorter side of the opening, and height is the depth from the opening to the bottom. Measure your product with anything packed around it, then add a small allowance.
Step by step
Gather the product and packing materials
Put together everything that goes in the box: the product, any inner carton, insert, tissue paper, cards or samples. The box must fit the whole packed set, not just the product.
Measure the length
With the box opening facing up, measure the longer side of the opening. For a product, measure its longest horizontal side as it will sit in the box.
Measure the width
Measure the shorter side of the opening, at a right angle to the length.
Measure the height
Measure the depth from the opening down to the bottom, or the product's height as it will stand in the box.
Add an allowance
Add a small allowance so the product slides in without forcing, but not so much that it moves around. Discuss the right allowance with your supplier.
Write it as L x W x H and confirm
Record the inside dimensions in the order length x width x height, state the unit (inches or millimeters), and confirm them on the dieline and proof.
Why inside dimensions matter
Packaging suppliers make custom boxes to the inside dimensions you give them, because that is the space your product needs. Outside dimensions are larger, since they include the thickness of the board. The difference is small for thin paperboard and more noticeable for corrugated or rigid boxes, so always say which measurement you are giving. When you order from Vorex, boxes are made to your exact size, and a specialist can review your measurements before quoting.
The standard order: L x W x H
The packaging industry lists box sizes as length x width x height. Getting the order right matters, because a 10 x 4 x 2 inch box and a 10 x 2 x 4 inch box open on different faces.
- Length (L): the longer side of the opening.
- Width (W): the shorter side of the opening.
- Height (H): the depth, measured from the opening to the bottom.
For tuck end cartons, the opening is at the end where the tuck flap closes, so the height is often the tallest dimension. For mailer boxes, the opening is the lid, so length and width describe the footprint and height is the depth.
How to measure your product
Use a rigid ruler or a digital caliper rather than a soft tape where possible, and measure at the widest points. Bottles with caps, jars with lids and products with handles should be measured at their largest point. If your product varies slightly from unit to unit, measure several and use the largest.
Include everything that goes inside
- Inserts, trays or dividers that hold the product.
- Inner cartons, pouches or bottle boxes.
- Tissue paper, crinkle fill, thank-you cards and samples.
- Instruction leaflets or warranty cards.
A common approach is to pack a sample set by hand into a temporary box and measure the packed bundle.
How much allowance to add
The product should go in and come out easily without sliding around. Too tight, and the box may bulge or be hard to close. Too loose, and products can shift and get damaged, and you may need extra void fill. The ideal allowance depends on the material and the product, so discuss it with your supplier and test a sample when fit is critical.
Common measuring mistakes
- Mixing units: state inches or millimeters clearly and use one unit throughout.
- Swapping width and height: check which face of the box opens.
- Measuring outside an existing box: if you copy a box you already use, measure inside it.
- Forgetting inserts: an insert can take up a meaningful amount of space.
- Ignoring shipping: many carriers charge by dimensional weight, so an oversized box can raise postage.
Measuring for bags and sleeves
Bags are usually listed as width x height, plus gusset depth if they expand. Sleeves are measured from the outside of the box or tray they cover, since they slide over it. If you are unsure which dimensions to give, describe the product and send photos, and a specialist can help work it out.
Check the dieline and proof
Before production you will see your dimensions on the dieline and the digital proof. Check them against your notes one last time. A small error caught at this stage is easy to fix; once the boxes are cut, it is not.
