Ask any packaging buyer about the most common mistake and the answer is usually the same: the box is the wrong size. Too big, and the product rattles around and the parcel costs more to post. Too small, and the product will not fit, or it fits so tightly that it gets squashed or marked.
Getting the size right is not difficult, but it does need a little care. This guide walks you through how to measure, what to allow for and how to check before you place a full order.
Start with the product, not the box
Measure the product itself, not a guess or a catalogue figure. Use a ruler or callipers, and measure three things:
- Length: the longest side.
- Width: the second longest side.
- Depth (or height): the thickness of the product.
Write them in the same order every time. Boxes are usually described as length x width x depth, and mixing the order is an easy way to end up with a box that is the wrong way round.
If the product is not a neat rectangle, such as a bottle, a candle or a pump dispenser, measure the widest point of each dimension. A bottle’s cap or a jar’s lid often sticks out further than the body, so measure the whole item, lid included.
Internal size vs external size
This is where many first-time buyers go wrong. A box has two sets of measurements:
- Internal size: the space inside, where the product sits.
- External size: the outside of the box, which is larger because the board has thickness.
When you order, you should give the internal size you need, since that is what has to fit your product. The board thickness is then added on top, so the outside will be bigger. This matters most for rigid boxes, where the walls are thick. Our guide to greyboard thickness explains how thickness changes the finished size.
Allow for a small amount of space
A box that matches the product exactly is rarely right. You need a small allowance so the product can go in and come out without scraping the printed finish. How much depends on the product and the box style. As a general rule:
- Rigid boxes and boxes with lids need a little room so the lid closes without catching.
- Tuck-end cartons need space for the flap to close neatly.
- Soft products, such as clothes, compress and need less precise sizing.
Rather than rely on a general rule, the safest way to confirm is a sample. We cover samples below.
Add space for inserts and padding
If your box includes an insert, the box has to be bigger to fit it. An insert is thickness added inside the box, and a moulded or cut insert can take up a surprising amount of space.
- A thin card insert adds very little.
- A foam or moulded pulp insert is thicker, and the product sits in a cut-out rather than on a flat surface.
Our guide to rigid box inserts compares the materials, and our insert boxes and die-cut insert boxes pages show what is possible. Decide on the insert first, then size the box around it.
Think about how the box will travel
If the box is going in the post, the size affects cost and protection.
- Oversized boxes cost more to post and leave room for the product to move.
- Right-sized boxes hold the product steadily, and are usually more economical to send.
- Slim, flat items may suit a mailer box or a bubble lined mailer rather than a full box.
- Rolled items suit mailing tubes.
For parcels, see our shipping boxes, flat pack mailing boxes and e-commerce packaging boxes. Check the size and weight limits your carrier uses, because crossing a size band can change the price.
Preview the shape before you order
Numbers on a page do not always show how a box will look. The Box Studio lets you preview a shape and size, which helps you spot a problem, such as a box that looks too tall for the product, before you commit.
Order a sample first
A sample is the cheapest way to catch a mistake. Before a full run:
- Place your real product inside, with its insert if it has one.
- Close the box and check that it sits properly.
- Open and close it a few times to check that nothing catches.
- If it will be posted, pack it as you would for a customer and test it with your carrier.
Fixing a size problem at sample stage costs far less than fixing it after the full order has been printed.
Common sizing mistakes
- Measuring the product but forgetting the lid, cap or packaging it comes in.
- Giving the external size when the internal size was needed.
- Forgetting that an insert takes up space.
- Ordering a “standard” size that is close but not quite right.
- Not checking the size against a carrier’s price bands.
What to send us for an accurate quote
The more precise your measurements, the better the result. Please send:
- Product length, width and depth, measured at the widest points.
- Whether the box needs an insert, and what kind.
- The box style you have in mind, or how you want it to open.
- Your artwork, if you have it.
- The quantity you need.
Request a quote and we will reply within 24 hours. Orders start from 100 units, free design support is included, you approve a digital proof before anything is printed, and delivery is free across the UK within 21 days of artwork approval. You can also browse our product range or read about the types of rigid boxes available.
FAQs (4)
Should I give the internal or external size?
Give the internal size, since that is the space your product has to fit. The external size will be larger because of the board thickness.
How much extra space should I allow?
It depends on the product and box style. A small allowance is normal, but the safest check is a sample with your real product.
Does an insert change the box size?
Yes. An insert takes up space inside the box, so decide on it before you finalise the size.
What is the minimum order and how long does delivery take?
Orders start from 100 units. Delivery is free across the UK and takes place within 21 days of artwork approval.