Packaging resources
Custom Packaging Size Guide
How to measure a product for packaging, what clearance to allow, how dimensions are quoted by format, and why small size changes affect price.
Sizing errors are the most common reason a first packaging order does not work. Almost all of them come from measuring the wrong thing, or from measuring the product in a state it will never be packed in.
Measure the product correctly
Measure at the widest point in all three dimensions, with the product in the state it will actually be packed.
A folded garment expands as it relaxes, so measure the stack under light compression rather than pressed flat. A jar has a lip wider than its base. A bottle with a pump fitted is taller than the bottle specification suggests. A boxed item inside another box needs the outer measurement, not the product.
Weigh it too. Weight decides board grade, and board grade slightly changes internal dimensions.
Allow the right clearance
Too tight and the pack will not close. Too loose and the product moves in transit.
| Situation | Clearance |
|---|---|
| Rigid product, snug fit | 1 – 2 mm each side |
| Product with an insert cavity | 1 – 2 mm around the cavity |
| Soft goods in a mailer | 5 – 10 mm each side |
| Fragile item needing void space | 15 – 25 mm plus cushioning |
Clearance is per side, so a 2 mm allowance adds 4 mm to the overall internal dimension.
How dimensions are quoted by format
Conventions differ, and getting them mixed up produces packaging in the wrong proportions.
- Boxes and cartons — length × width × height, internal dimensions
- Paper bags — width × gusset × height
- Pouches — width × height, plus bottom gusset where present
- Mailers — internal usable dimensions, not the outer size
- Sleeves — circumference of the filled product plus a glue lap
- Labels — width × height of the die, not the liner
- Trays — top opening × depth
Always confirm whether a supplier is quoting internal or external dimensions. On corrugated the difference is several millimetres per wall.
Practical size ranges
These are efficient ranges rather than limits. Anything is possible; some things are expensive.
| Format | Common range |
|---|---|
| Folding carton | 2 × 2 × 2 in to 12 × 10 × 6 in |
| Rigid box | 4 × 4 × 2 in to 14 × 10 × 4 in |
| Mailer box | 6 × 4 × 2 in to 16 × 12 × 4 in |
| Corrugated shipper | 6 × 6 × 4 in to 24 × 18 × 12 in |
| Paper bag | 5 × 3 × 8 in to 16 × 6 × 12 in |
| Stand-up pouch | 3.5 × 5 in to 12 × 16 in |
Why small changes affect price
You buy sheet area, not boxes. The manufacturer fits as many flat dielines as possible onto a press sheet, and the sheet cost divides by how many fit.
A half inch that pushes the layout from eight-up to six-up raises material cost by a third with no visible benefit. Ask whether a small dimensional change nests better — sometimes a quarter inch costs nothing in function and saves real money.
Dimensional weight
For anything shipped to consumers, carriers charge on the greater of actual weight and volumetric weight. An oversized mailer costs money on every order, permanently.
Reducing a mailer by an inch often saves more across a year of shipping than any material change, which makes right-sizing both the cheapest and the most environmentally useful decision available.
Confirm with a sample
Order a plain structural sample and put the actual product inside it. Close it, lift it, shake it gently. Rattling means an insert is needed; a straining lid means the dieline is tight.
The sample costs very little. Discovering the problem after a production run costs the run, and the way tooling and setup costs behave explains why a resize after tooling is more expensive than it first appears.
Measuring properly
Most fit failures come from measuring the wrong thing rather than measuring inaccurately.
Measure at the widest point. Bottles are frequently widest at the shoulder rather than the base. Jars are often widest at the lid. A carton sized to the body of either will not close.
Measure as it ships. Pumps that lock down for transit and pumps that do not differ by an inch or more. A garment folded one way is a different object from the same garment folded another.
Include everything that goes in. A leaflet, a sachet, a desiccant pack and tissue all take space that nobody accounted for.
Measure several units. Handmade and natural products vary between batches. Size to the largest in a typical batch, not the one sample on your desk.
Clearance, and where it goes wrong
Clearance is specified per side. Two millimetres of clearance on a 60 mm product produces a 64 mm internal dimension, not 62 mm. Confusing the two is the most common sizing error we see.
How much depends on the product. Rigid items with consistent dimensions need very little. Anything that flexes, varies between units or has to be inserted quickly at a packing bench needs more. Foam cavities need less than board because foam compresses.
There is also a floor. A cavity cut with no clearance at all cannot accept the product, because manufacturing variance exists on both sides.
Sheet nesting
You buy sheet area, not boxes. The manufacturer fits as many flat dielines as possible onto a press sheet, and the sheet cost divides by how many fit.
A half inch that pushes the layout from eight-up to six-up raises material cost by a third with no visible benefit. Ask whether a small dimensional change nests better — sometimes a quarter inch costs nothing in function and saves real money.
This only works if you ask before the die is cut. Once tooling exists, a resize means new tooling.
Dimensional weight
For anything shipped to consumers, carriers charge on the greater of actual weight and volumetric weight. An oversized mailer costs money on every order, permanently.
Reducing a mailer by an inch often saves more across a year of shipping than any material change, which makes right-sizing both the cheapest and the most environmentally useful decision available.
The practical test is how much void fill goes into a typical parcel. Void fill is a direct measure of volume you are paying to ship and doing nothing with.
Confirm with a sample
Order a plain structural sample and put the actual product inside it. Close it, lift it, shake it gently. Rattling means an insert is needed; a straining lid means the dieline is tight.
The sample costs very little. Discovering the problem after a production run costs the run, and the way tooling and setup costs behave explains why a resize after tooling is more expensive than it first appears.