April 21 2026
Every business that ships products has dealt with the same problem at some point. The boxes you can buy off the shelf are either slightly too big, slightly too small or the wrong shape entirely. You end up stuffing void fill into oversized boxes, taping awkward combinations together or accepting that your product is going to rattle around in transit.
Custom size cardboard boxes solve this problem completely. Instead of forcing your products into standard dimensions, you get boxes made to your exact specifications. The result is better protection, lower shipping costs and a more professional presentation when your customer opens the delivery.
If you have been putting off ordering custom sizes because you assumed the minimum orders would be huge or the lead times too long, this guide will set the record straight. We will cover how custom sizing works, what it costs, how to measure your products properly and what to look for in a supplier.
Standard boxes come in set dimensions that are designed to cover a broad range of uses. They work reasonably well for some products, but for anything with unusual proportions, fragile components or premium branding, they create problems.
When a box is too big for the product inside, you need void fill to stop things moving. That means buying bubble wrap, paper, packing peanuts or foam inserts. Each of those adds cost per order. But there is a bigger expense hiding in plain sight. Oversized boxes mean you are paying for more postage than you need to.
Royal Mail and most courier services price parcels based on both weight and dimensions. A box that is 10cm wider than necessary could push you into a higher pricing band. Multiply that across hundreds or thousands of shipments per month, and the numbers add up quickly.
Products that move around inside their packaging during transit are more likely to arrive damaged. Damaged goods mean returns, replacements and unhappy customers. A snug-fitting box with the right level of cushioning keeps everything secure without relying on excessive filler materials.
Your packaging is the first physical interaction a customer has with your brand. A box that looks like an afterthought, too big with crumpled paper stuffed around the product, does not inspire confidence. A clean, well-fitted box with your branding on it tells the customer you care about the details.
The process is more straightforward than most people expect. Here is how it works at Boxtopia.
You need three measurements: length, width and height. Always measure the product at its widest, tallest and longest points. If you are shipping multiple items in one box, measure the arrangement you plan to use.
Add a small allowance for cushioning material. Typically 10 to 20mm on each side is enough for most products. If the item is fragile, you may want a bit more room for protective wrapping.
The most common styles are Regular Slotted Containers (RSC), which are the standard box with four flaps that meet in the middle, and die-cut boxes, which are cut and scored from a single sheet and fold into shape without staples or glue. Die-cut boxes tend to look neater and work well for retail or subscription packaging.
For postal applications, mailer boxes with a tuck-in lid are popular because they create a clean unboxing experience.
This determines how strong the box is. Single wall corrugated board is suitable for lighter items up to around 10kg. Double wall offers significantly more strength and crush resistance, making it the right choice for heavier products, fragile goods or anything that needs to survive stacking in a warehouse.
Your supplier should be able to recommend the right grade based on what you are packing and how it will be shipped.
With Boxtopia, you can order custom size boxes with no minimum order quantity. That means you can order 10 boxes or 10,000. Our box calculator lets you input your dimensions online and get an instant quote. If you need help choosing the right specification, our team can advise.
This is the question everyone asks, and the answer depends on several factors.
Like most manufactured products, the unit price drops as the quantity increases. But unlike many suppliers, we do not require minimum orders of 500 or 1,000 units. If you need 25 custom boxes to test a new product line, you can order 25.
Double wall board costs more than single wall because it uses more material. The difference is usually modest, and for heavier products it pays for itself by reducing damage.
A simple RSC box is generally the most affordable option. Die-cut boxes cost a little more because the tooling is more complex, but they offer a cleaner look and easier assembly.
Plain brown cardboard is the most economical choice. Adding custom printing, whether that is a simple one-colour logo or full CMYK artwork, increases the cost per unit. We cover printing options in more detail in a separate guide.
As a rough benchmark, a custom-sized single wall RSC box in a modest quantity often costs between 50p and £2 per unit depending on size and specification. Volume orders bring the price down significantly.
People new to custom packaging tend to make a few predictable errors. Knowing what they are helps you avoid them.
If you measure your product and order a box that is exactly the same dimensions, there will be no room for any protective material. Always add your cushioning allowance before finalising the box size.
A single wall box might seem fine for your product, but if those boxes are going to be stacked on pallets or shipped long distances via multiple handling points, they may not hold up. Ask your supplier for advice if you are unsure.
If you ship via Royal Mail, your box dimensions determine which pricing band you fall into. Small Parcel, Medium Parcel and Large Parcel each have specific size limits. Getting your box dimensions just right can keep you in a lower band and save a meaningful amount on postage.
For Royal Mail Small Parcel, the maximum dimensions are 61cm x 46cm x 46cm with a maximum weight of 2kg. Designing your box to fit within these limits can make a real difference to your shipping costs.
It is tempting to go for the thickest board and the most complex box style, especially when you are worried about damage. But over-packaging is wasteful and expensive. Match the packaging to the product. A pair of socks does not need double wall corrugated board.
Off-the-shelf boxes are cheaper per unit at small quantities because there is no setup involved. If you ship a handful of orders per month and your products happen to fit a standard size reasonably well, standard boxes may be all you need.
But as soon as your order volume grows, the economics shift. The money you save on void fill, reduced postage costs and fewer damaged shipments often more than covers the small premium for custom sizing. And the improvement in presentation is immediate.
For businesses shipping 50 or more orders per week, custom size boxes almost always make financial sense.
Lead times vary by supplier and specification. For plain custom-sized boxes with no printing, turnaround is typically fast. At Boxtopia, most plain box orders ship within a few working days. Printed boxes take a little longer because of the artwork approval and printing process, but even then, you are usually looking at one to two weeks for standard orders.
If you have a product launch or seasonal peak coming up, it pays to order ahead. But for ongoing restocking of a box size you have ordered before, reordering is quick and straightforward.
If you are still using standard boxes and dealing with the compromises that come with them, switching to custom sizes is one of the simplest improvements you can make to your packaging process.
Start by measuring your best-selling products. Use our online box calculator to see what custom sizing would look like for your specific needs. And if you want to talk it through, our team is here to help. We have been making custom cardboard boxes in the UK for over 25 years, with no minimum order and free delivery on every order.
If this is your first time ordering custom size boxes, ask your supplier for a sample before committing to a full run. Most reputable manufacturers will send a plain sample at cost so you can test the fit with your actual product. Check the internal dimensions against your item plus any padding or tissue paper you plan to use inside. A box that looks perfect on a spec sheet can feel too tight once you add protective wrapping. Always allow 5-10mm of clearance on each side for comfortable packing. Once you have confirmed the size works, scaling up your order is straightforward and the per-unit cost drops quickly at higher quantities.
