custom sizes

custom sizes means your box is made to the dimensions of your product and packing method instead of forcing your product into a stock carton. Custom Postal Boxes makes boxes in custom sizes in house in Wolverhampton, covering postal, mailer and shipping formats, with low minimum order quantities, free design support and free UK delivery on quote based orders.

Why custom sizes improve protection and cost control

A box that fits closely holds the product steady, so less fill is needed and the contents arrive without the scuffs and dents caused by sliding. It also removes the hidden costs of a poor fit, including extra board, extra fill, slower packing and parcels tipping into a higher postage band because of a few wasted centimetres. Over hundreds of orders those small savings repeat.

Custom sizing applies across the range, from small postage boxes to custom shipping boxes. The principle is the same at every scale. Measure honestly, allow for protection and choose a size your packing team can repeat quickly and consistently.

How to measure for custom sizes

Start with the product in its retail pack if it has one, because that is what the box must hold. Measure length, width and height at the widest points, including lids, caps, handles or cables that stick out. Then decide how much protection each face needs and add that allowance to reach the internal box dimensions you should quote.

Internal and external dimensions explained

Box sizes are normally quoted as internal dimensions, meaning the usable space inside. External dimensions are larger by roughly the board thickness on each side, and external size is what postal services measure. When a postal band matters, work backwards from the external limit, using the Royal Mail size information for tracked services as a reference, so the finished packed box stays inside it.

Allowing for inserts and wrapping

Inserts, tissue, sleeves and protective wraps all consume space that a bare product measurement misses. Measure the product fully dressed as the customer will receive it, or add the thickness of each extra layer to every affected side. A trial pack with real materials is the most reliable check before a full order.

Choosing which products deserve a custom size

Not every product needs its own box. Start with your highest volume line, your most fragile line and any line where a stock box pushes postage into the next band, because those gain most from an exact fit. Products that sell together can share a sized box when the common combinations are mapped first.

Reducing packaging waste with a closer fit

Right sizing is one of the simplest ways to use less material, since a smaller box needs less board and less fill and takes less vehicle space. That aligns with the direction of the GOV.UK producer responsibility guidance for packaging, which encourages producers to reduce unnecessary packaging and design for recycling. Customers notice the difference too, because a neat box is easier to open, store and recycle at home.

Ordering boxes in custom sizes

Share your internal dimensions, product weight and quantity via the contact page for a quote and you will receive pricing based on size, material and quantity, with free design support included. If you are unsure which format suits you, browse the shop or the packaging materials category to compare postal, mailer and shipping styles before you decide.

FAQs about custom sizes

How do I work out the custom size I need?

Measure your product at its widest points as it will be packed, then add allowance for wrapping or inserts to reach the internal box size. A trial pack with real materials confirms the fit before you order in quantity.

Are box sizes quoted as internal or external dimensions?

They are normally quoted as internal dimensions, which describe the usable space inside the box. External dimensions are slightly larger and are the measurements postal services use, so both matter when a size band applies.

Can custom sizes lower my postage costs?

Yes, when a closer fit keeps the packed parcel inside a lower postal or courier band. Removing a few centimetres of empty space can change the band, and it also reduces the fill you need to buy.

Do I need a different custom size for every product?

No. Most sellers size boxes for their highest volume and most fragile lines and group similar products into shared sizes. Mapping common order combinations helps you keep the size list short and packing simple.