How to measure your product for a box
By the Packaging Workshop team · Updated · 6 min read
Box sizes are given as length × width × height, measured inside the box. Measure the product at its widest points, then add a small clearance so it slides in without forcing.
Which side is which
Stand the product as it will sit on the shelf. Length is the width of the front panel, left to right. Width is the depth of the side panel, front to back. Height runs from the base to the opening.
For mailers and trays the convention changes slightly: length and width describe the base, and height is the wall height. Each style page in PW Studio explains what L, W and H mean for that structure.
Tools that give a reliable number
A digital caliper is the most accurate tool for small products, and a steel rule for larger ones. Soft tape measures stretch and curve, so avoid them for anything under about 300 mm. Measure twice, and measure several products if they come from production rather than a sample, because real products vary.
How much clearance to add
As a starting point for folding cartons:
- Rigid products such as jars or bottles: 1 to 2 mm on each dimension.
- Soft or flexible products: 0 to 1 mm, so they do not move.
- Products with an insert or tray: measure the insert, then add 1 mm.
- Corrugated shippers: 3 to 5 mm, or more if you add void fill.
- Rigid gift boxes: 3 to 5 mm, because their walls do not flex at all.
Measuring awkward shapes
Bottles: measure the widest point, usually the shoulder or the base, not the label. Include pumps, droppers and caps in the height.
Round products: use the diameter for both length and width.
Irregular products: lay the product in the position it will travel and measure the smallest rectangle it fits into. An insert can then stop it moving.
Multiple items: arrange them as they will be packed, then measure the group, not each item.
Common measuring mistakes
Measuring the label rather than the bottle shoulder, forgetting a pump or dropper cap, and measuring the outside of an existing box when you need inside sizes. If you copy a box you already have, measure inside it, wall to wall.
Another common slip is mixing units between suppliers. PW Studio stores every size in millimetres and converts on screen, so you can type in inches and still export exact millimetre geometry.
Check before you print a run
Print the dieline at 100 % on paper or card, cut it out and fold it around the product. It takes ten minutes and catches most fit problems. For important launches, ask your printer for a blank sample in the real board.
Common questions
Are PW Studio sizes inside or outside dimensions?
Inside. The engine adds board thickness for the outside panels.
Should I measure in millimetres or inches?
Either. The studio switches between mm, cm and inches, and stores everything in millimetres so nothing is lost in rounding.
What if my product is round?
Use the diameter for both length and width. A square carton around a round product leaves corner space you can use for an insert.
How do I find the outside size for shipping rates?
Add about two board thicknesses to each inside dimension: roughly 1 mm for 18 pt carton board, 3 mm for E-flute and 6 mm for B-flute corrugated.