Blog
Jun. 01, 2026
If you want to order custom packaging, you need to know how to measure a box correctly. Box size may look simple, but small mistakes can cause big problems. A box may become too tight. A product may not fit. Shipping cost may increase. Artwork may also be placed in the wrong direction.
Before production, we always confirm the box size, box structure, material, and product size. These details help us create packaging that looks good, protects the product, and works well in real use.
This guide explains the height width and length of box in a clear way. You will learn what length, width, and height mean, how to measure a box step by step, and how to avoid common mistakes when ordering custom packaging.
Box dimensions are usually written as Length × Width × Height, or L × W × H.
Length is usually the longest side of the box opening. Width is the shorter side of the opening. Height is the vertical distance from the bottom to the top of the closed box.
For example, 300 × 220 × 80 mm means:
Length: 300 mm
Width: 220 mm
Height: 80 mm
This order is important for custom packaging. It affects the box structure, opening direction, insert layout, and artwork position. To avoid mistakes, always confirm the size order and unit with your packaging supplier before production.
Measuring a box is easy when you follow the correct order.
If the box is foldable, assemble it before measuring. A flat dieline is not the same as the finished box size.
For example, a folding carton includes flaps, glue areas, fold lines, and tuck parts. If you only measure the flat sheet, you may not get the actual finished size.
Put the box on a table. Keep it in its natural position. Do not press it, bend it, or tilt it.
If the box has an opening, place it with the opening facing up. This makes it easier to identify the length and width.
Find the longest side of the box opening. Measure from one edge to the opposite edge.
Write this number first.
Measure the shorter side of the box opening. This number comes second.
Measure from the bottom of the box to the top. This number comes third.
The final size should be written as:
Length × Width × Height
For example:
300 × 220 × 80 mm
Step 6: Confirm the Unit
Always write the unit clearly. You can use mm, cm, or inches.
For international custom packaging, millimeters are usually better. They are more accurate and easier for factories to work with.
Different box types may need different measuring methods. A folding carton, rigid box, drawer box, and shipping carton do not always use the same size logic. The table below gives a quick reference.
| Box Type | Best Dimension to Confirm | What to Measure | Common Use |
|---|---|---|---|
| Folding Carton Box | Finished size or inner size | Length × Width × Height after folding | Cosmetics, food, medicine, small retail products |
| Rigid Gift Box | Usually inner size | Inner usable space, lid size, base size | Luxury gifts, tea boxes, beauty sets |
| Drawer Box | Inner tray size and outer sleeve size | Drawer size, sleeve size, and sliding direction | Jewelry, cosmetics, premium packaging |
| Mailer Box | Inner size | Usable space after folding | E-commerce products and subscription boxes |
| Shipping Carton | Outer size | Closed carton length, width, and height | Bulk shipping and freight calculation |
| Book Style Box | Inner size | Product space plus room for easy removal | Books, notebooks, catalogs, gift sets |
This is one of the most important points in box measurement.
A box can have two kinds of dimensions:
This means the usable space inside the box.
This means the total outside size of the box.
For product fit, internal dimensions are usually more important. For shipping, storage, and carton calculation, external dimensions are usually more important.
If your product is 200 × 150 × 40 mm, the internal box size should be slightly larger than the product. You may need extra space for tolerance, inserts, tissue paper, or protective padding.
But if you are calculating shipping cost, the shipping company usually cares about the outside size of the closed box.
For custom packaging, always tell your supplier whether your size is internal or external.
A clear format is:
Internal size: 300 × 220 × 80 mm
or
Outer size: 300 × 220 × 80 mm
This small detail can prevent many production mistakes.
Different box structures need slightly different measurement details.
A folding carton is usually made from paperboard. It is common for cosmetics, food packaging, medicine packaging, small gifts, and retail products.
Measure the finished box after folding. Do not only measure the flat dieline.
For folding cartons, the supplier also needs to know the opening style, tuck direction, glue position, and material thickness.
A rigid gift box is made with thick greyboard and wrapped with printed paper. It feels stronger and more premium than a normal folding carton.
For rigid boxes, internal size is very important because the board has thickness. If you only provide the outside size, the usable space inside may be smaller than expected.
For a lid and base rigid box, the lid size and base size may also be different. The lid is usually slightly larger so it can fit over the base.
A drawer box includes an outer sleeve and an inner tray. It is often used for jewelry, cosmetics, gift sets, and premium packaging.
When measuring a drawer box, confirm three details:
Outer sleeve size
Inner drawer size
Pulling direction
The drawer must slide smoothly. If the fit is too tight, the customer may struggle to open it. If it is too loose, the box may feel cheap.
A mailer box is often used for e-commerce shipping and subscription packaging. It is usually made from corrugated paper.
For mailer boxes, measure the usable inside space after folding. The box must have enough room for the product, tissue paper, cards, padding, or inserts.
A shipping carton is used for transport. It is usually measured by outside dimensions because freight companies use carton size to calculate volume and dimensional weight.
A larger carton may cost more to ship, even if it is light. This is why box size should not be too large for the product.
To measure a box for shipping, close the box first.
Then measure the outside:
Length: longest side
Width: shorter side
Height: vertical side
Shipping companies often calculate cost based on actual weight or dimensional weight. Dimensional weight is based on box volume.
So a box that is too large may increase shipping cost. This matters for e-commerce brands, wholesale buyers, and bulk packaging orders.
For custom packaging, you should measure the product first.
Then decide how much extra space the box needs.
You may need extra space for:
Paper insert
Foam insert
Blister tray
Tissue paper
Bubble wrap
Ribbon puller
Product tolerance
Easy product removal
For example, if a hardcover book measures 210 × 150 × 25 mm, the inner size of the box may need to be around 215 × 155 × 30 mm. This gives the book enough room and makes it easier to take out.
If you add a paper tray or ribbon, the supplier may adjust the size again.
Always use:
Length × Width × Height
Do not switch the order unless you clearly explain it.
This is a common problem. For custom packaging, it can cause the box to be too small or too large.
Always mark internal size or outer size.
Product size is not always the same as box size. You need extra space for tolerance and packaging structure.
Rigid boxes, corrugated boxes, and paperboard boxes all have different material thickness. This affects the usable inside space.
If your box has an insert, the product must fit inside the insert, not just inside the box.
A cosmetic bottle may fit in the box alone, but it may not fit after adding a paper holder.
The standard order is length × width × height. Length comes first, width comes second, and height comes third.
L × W × H means length × width × height. It is the standard way to describe box dimensions.
The length is usually the longest side of the box opening. For some special lid-connected boxes, the opening direction may also affect how the length is defined.
For product fit, measure the inside. For shipping and storage, measure the outside. For custom packaging, always tell your supplier which one you are using.
Close the box and measure the outside length, width, and height. Shipping companies use these dimensions to calculate volume and dimensional weight.
No. The box should usually be slightly larger than the product. You need space for tolerance, inserts, protection, and easy use.
Millimeters are best for custom packaging production. Inches are also common in some markets, but always keep the unit clear.
If you are planning a custom gift box, folding carton, mailer box, drawer box, shipping carton, or paper packaging project, our team can help you confirm the right box size and structure. Share your product size, box type, quantity, and design details through our Contact Us page, and we will help you create practical custom packaging for your product.
