How to Measure Your Product and Give Inner vs Outer Box Dimensions (L×W×H)

Why “inner” and “outer” give different boxes

Every box wall has thickness. Inner dimensions describe the empty space your product sits in; outer dimensions describe the space the closed box takes up. The gap between them depends on the material: it is small for a thin paperboard carton, larger for corrugated board, and larger again for a rigid box whose lid fits over the base. If a supplier reads your outer size as an inner size (or the other way round), the box is either too tight to close or loose enough for the product to rattle.

Most packaging suppliers quote and draw dielines on inner dimensions, because product fit is the main risk. Carriers, warehouses and retailers, on the other hand, care about the outside. That is why a size such as “100 × 60 × 150 mm” without the word inner or outer is one of the most common causes of a re-made sample.

Step-by-step: measuring the product

1. Use the finished, filled product. Measure the actual bottle, jar or device with cap, pump, label and any shrink sleeve, not the drawing of the empty container.
2. Measure at the widest points. Use a digital caliper for small items and a steel rule or tape for larger ones. Shoulders, lids and handles are often wider than the body.
3. Measure several units. Bottles, glass jars and hand-made items vary. Take the largest reading, not the average.
4. Decide the orientation. Decide which face goes up and which face meets the opening. That fixes which measurement becomes length, width and height.
5. Add clearance once. For a snug folding carton, a total allowance of about 1–3 mm per dimension is common. Mailer boxes, fragile products, soft goods and items that slide into a sleeve usually need more, sometimes several millimeters. If you add the clearance yourself, tell the supplier so it is not added twice, and confirm the final allowance on a sample.
6. Measure the insert, not the product, when an insert is used. If the product sits in a card, pulp or foam insert, the box inner size is set by the insert’s outer size. Our insert and inner tray guide covers how insert walls add to the size.

Writing L×W×H in the right order

The common packaging convention is length × width × height. Picture the box with its opening facing you: length is the longer edge of the opening, width is the shorter edge, and height (some suppliers say depth) runs from the opening to the opposite end. For a tuck end carton the opening is the tuck flap end, so a tall cosmetic carton may read 40 × 40 × 150 mm. For a mailer box or a two-piece rigid box the opening is the large top face, so the same logic gives something like 250 × 180 × 60 mm.

The order matters because it decides where the flaps, glue tab and artwork panels fall on the dieline. You can see how the opening defines the measurements on our tuck end box dieline and mailer box dieline pages.

When to give outer dimensions instead

• Choose inner dimensions when product fit and presentation matter most, which is true for most retail and gift boxes.
• Choose outer dimensions when the box must fit a fixed space: a retail shelf or peg, a display tray, a shipper carton you already buy, a drawer, or a courier size band.
• When both matter, give the controlling figure and a limit for the other, for example: “inner 120 × 80 × 40 mm minimum, outer must not exceed 128 × 88 × 46 mm”. The supplier can then tell you whether the chosen material allows both.
• For e-commerce shipping, carriers measure the outside of the package, so outer size also drives dimensional weight. See the dimensional weight and box sizing guide before you lock the size.

What to send in your RFQ

1. Box style (for example tuck end, mailer, magnetic rigid box) and a reference photo if you have one.
2. Product dimensions as measured, product weight and the number of items per box.
3. Box dimensions in mm, labeled “inner” or “outer”, in L×W×H order, and whether clearance is already included.
4. Insert requirement and material, if any.
5. Any outer size limit (shelf, shipper carton, courier band).
6. Quantity (MOQ is 500 PCS) and whether you can send a physical product sample for fit testing.

For general box options, see custom boxes and custom packaging boxes.

Common measuring mistakes

• Measuring an old box from the outside and sending it as the inner size, which makes the new box too large.
• Measuring a flat, unfolded box instead of an assembled one. Flat sizes belong to the dieline, not to the box specification.
• Mixing inches and millimeters or rounding fractions of an inch; give millimeters to one decimal place if the fit is tight.
• Swapping width and height, which moves the opening to the wrong face and changes the artwork layout.
• Forgetting the insert or a product leaflet, which can take several millimeters of space.
• Adding clearance twice, once by the buyer and again by the supplier.
• Skipping the plain sample. A plain or white sample made to the dieline is the cheapest way to check fit before printing; confirm the sampling option in the quotation.

Related pages

• Custom boxes
• Custom packaging boxes
• Tuck end box dieline
• Mailer box dieline
• Dimensional weight and box sizing guide
• Contact Lisa for a quote