Short answer: choose a single wall cardboard box when the contents are light to moderate in weight, not especially fragile, and the box will make one trip through the post or courier network. Choose a double wall cardboard box when the contents are heavy, breakable or valuable, when the box will be stacked under other boxes, or when it will be handled several times, as in a house move or storage. Most online sellers need both: single wall for the bulk of everyday orders and a smaller stock of double wall for the heavy and delicate ones.
The rest of this guide explains what the two constructions actually are, how to judge which one your products need, where people commonly overspend or underspend, and how to work out a sensible mix of stock. Where we mention Pack Solution products, the sizes and pack details come from our current product listings.
Contents
- What is the difference between single wall and double wall?
- Side-by-side comparison
- How to decide: five questions to ask about each product
- A worked example: one shop, three products
- Sizes Pack Solution stocks in each
- Common buying mistakes
- What box construction cannot do on its own
- Questions buyers ask
What is the difference between single wall and double wall?
Both are made from corrugated board: flat paper sheets, called liners, glued to a wavy paper layer called the flute. The flute works like a row of tiny arches. It keeps the liners apart, which is what gives corrugated board its stiffness and its ability to absorb a knock without creasing straight through.
Single wall board has one fluted layer between two liners. It is light, folds easily and costs less per box. For a well-packed parcel that is not too heavy and makes a single journey, it is usually enough.
Double wall board has two fluted layers and three liners. The extra layer makes the board thicker and stiffer, so the box resists crushing from above and puncture from the side better than a single wall box of the same size. It is also heavier and takes up more space when stored flat, and each box costs more.
One point that is often misunderstood: "double wall" does not mean "twice as strong" in any precise sense. How a box performs depends on the paper grades used in the liners and flutes, the flute sizes, how well the box is closed and taped, and above all how it is packed. Two double wall boxes from different makers can behave quite differently. Our product listings describe the construction (one or two layers of fluting) but do not publish laboratory crush or burst ratings, so we do not quote weight limits for either range. If your application depends on a certified rating, for example a regulated or very heavy load, ask for the specific specification before you buy rather than relying on the words single or double wall.
Why the construction matters in transit
A parcel in a courier network is lifted, slid down chutes, sorted on conveyors, loaded into cages and vans and often has other parcels placed on top of it. Two kinds of force do most of the damage:
- Compression from above. Other parcels, or a stack in a warehouse, press down on the box. If the walls buckle, the contents take the load.
- Impact and puncture. A corner hits the floor, or something sharp meets the side panel. Thicker board spreads the impact and is harder to pierce.
Double wall board helps with both. Single wall board can cope with both too, provided the parcel is not heavy, the contents fill the box properly and the box is not stacked under heavy loads for long periods.
Single wall vs double wall: side-by-side comparison
The table below summarises the practical differences. It describes general tendencies, not guaranteed performance; packing quality matters as much as board choice.
| Factor | Single wall box | Double wall box |
|---|---|---|
| Construction | One fluted layer, two liners | Two fluted layers, three liners |
| Typical use | Everyday e-commerce orders, light goods, short-term storage | Heavy or fragile goods, high-value orders, house moves, stacked storage |
| Resistance to crushing | Adequate for light, well-filled parcels | Higher, better when stacked or handled repeatedly |
| Puncture resistance | Lower | Higher |
| Box weight | Lighter, which can matter near a weight band | Heavier |
| Storage space when flat | Less | More |
| Cost per box | Lower | Higher |
| Reuse for returns or moves | Sometimes, depending on condition | More likely to survive a second trip |
If you are unsure, the safest default is to ask what happens if the box fails. If failure means a cheap, robust item arrives with a dented box, single wall is fine. If failure means a broken product, a refund and a lost customer, the extra cost of double wall is usually small by comparison.
How to decide: five questions to ask about each product
Rather than choosing one box type for the whole business, go through your products and ask the same five questions about each. It takes a few minutes and usually shows that only a minority of orders need the heavier board.
1. How heavy is the packed parcel?
Weigh a typical order with its wrapping, not just the product. Heavier parcels put more strain on the base and seams, and they are more likely to be placed low in a cage with other parcels above. There is no single cut-off weight that applies to every box, because board grade and box size both matter. As a practical rule, the heavier and denser the contents, the more you should lean towards double wall, especially for larger boxes, where the panels have a longer span and flex more.
2. How fragile is it, and how is it protected inside?
Glass, ceramics, framed items and electronics need cushioning inside the box whatever board you use. The box stops crushing and puncture; the cushioning stops shock and vibration reaching the item. A fragile item in double wall board with no cushioning can still break. A fragile item well wrapped in small bubble wrap and held still in a single wall box may arrive safely on a short journey. For breakables, though, double wall gives you a margin for the knocks you cannot control.
3. Will the box be stacked?
Stacking is where single wall boxes most often let people down. A box that is fine on its own may slowly bow when other boxes sit on it for days in a stockroom or a removal van. If boxes will be stacked several high, or stored for weeks, double wall is the better choice for the lower boxes at least.
4. How many times will it be handled?
A parcel posted once and opened by the customer has an easier life than a box used for a house move, packed, carried, loaded, unloaded and then stored. Boxes that must survive several trips, or that customers may reuse for returns, benefit from the thicker board.
5. Does the extra weight or cost change anything?
Double wall boxes weigh more. For most parcels the difference is small, but if a parcel sits just under a courier's weight limit, a heavier box can tip it into the next price band. Check the packed weight with the box you intend to use. Equally, the cost difference per box is real across hundreds of orders, so it is worth using double wall where it earns its keep rather than everywhere.
A worked example: one shop, three products
The example below is illustrative. It is not a real customer, and the weights are assumptions chosen to show the reasoning.
Imagine a small homeware shop that sells three things: cotton tea towels, scented candles in glass jars, and cast-iron casserole dishes.
- Tea towels are light, soft and cannot break. They do not need a box at all; a grey mailing bag is cheaper and lighter. If the shop prefers a box for presentation, a small single wall box is plenty.
- Candles in glass jars are fragile but not heavy. Each jar is wrapped in bubble wrap and packed snugly. A single wall box can work for one or two jars on a single journey, but because glass breaks and returns are costly, many sellers choose double wall for multi-jar orders. A sensible approach is single wall for one jar and double wall for three or more.
- Cast-iron casserole dishes are heavy and dense, and the enamel can chip. These go in double wall boxes with cushioning on all sides and a layer under the base.
In this example most orders are tea towels and single candles, so the shop's stock might be roughly three single wall boxes for every double wall box. The exact ratio should come from the shop's own order history, which brings us to stock planning: count how many orders of each type you sent last month, map each to a box, and buy in proportion, with a little extra of the boxes you run out of most often.
Sizes Pack Solution stocks in each
Both ranges are supplied flat and sold per box, with a minimum of 5 boxes per size. Sizes below are length x width x height as listed on our product pages. Our single wall listing states its sizes as internal dimensions; check each product page before ordering if internal size is critical for your item.
Single wall cardboard boxes
Our single wall cardboard boxes currently come in these sizes:
| Size (inches) | Size (mm) | Typical use |
|---|---|---|
| 5 x 5 x 5 | 127 x 127 x 127 | Small gifts, mugs, candles |
| 6 x 6 x 6 | 152 x 152 x 152 | Small boxed items |
| 7 x 5 x 5 | 178 x 127 x 127 | Small, slightly longer items |
| 8 x 6 x 4 and 8 x 6 x 5 | 203 x 152 x 102 / 127 | Books, accessories, small electronics |
| 9 x 6 x 6 | 229 x 152 x 152 | Small multi-item orders |
| 10 x 8 x 6 | 254 x 203 x 152 | General small parcels |
| 12 x 9 x 4, 12 x 9 x 6, 12 x 9 x 9 | 305 x 229 x 102 / 152 / 229 | A4 items lying flat |
| 12 x 12 x 12 | 305 x 305 x 305 | Homeware, mixed orders |
| 15.35 x 11.6 x 7.3 (listed as Extra Strong) | 390 x 295 x 185 | Larger parcels needing a sturdier single wall |
| 17.7 x 13.7 x 6 | 450 x 350 x 160 | Made to the Royal Mail Small Parcel maximum |
| 18 x 10 x 5.5 | 457 x 252 x 143 | Long, shallow items |
| 24 x 18 x 18 | 610 x 457 x 457 | Large, light items and storage |
The 450 x 350 x 160mm size is worth knowing about if you post with Royal Mail. Royal Mail's size and weight guide sets the Small Parcel format at a maximum of 45cm long, 35cm wide and 16cm deep, with a 2kg weight limit. A box made to that outer size helps you stay within the format, but the packed parcel must still be within the weight limit and the measured dimensions, so check both before buying postage.
Double wall cardboard boxes
Our double wall cardboard boxes currently come in:
| Size (inches) | Size (mm) | Typical use |
|---|---|---|
| 9 x 6 x 6 | 229 x 152 x 152 | Small, heavy parts |
| 10 x 10 x 10 | 254 x 254 x 254 | Compact heavy items |
| 12 x 9 x 6 and 12 x 9 x 9 | 305 x 229 x 152 / 229 | A4 items flat, boxed goods |
| 12 x 12 x 12 | 305 x 305 x 305 | Books, kitchenware |
| 14 x 14 x 14 | 356 x 356 x 356 | General moving and storage |
| 18 x 12 x 11 | 457 x 305 x 279 | Larger heavy items |
| 18 x 18 x 18 | 457 x 457 x 457 | Bulky items, removals |
| 23 x 12 x 15 | 580 x 305 x 377 | Long items |
| 24 x 18 x 12, 24 x 18 x 18, 24 x 24 x 24 | 610 x 457 x 305 / 457, 610 x 610 x 610 | Large, light items such as bedding |
A note on very large boxes: the biggest double wall sizes are best for bulky but light contents. Filling a 24-inch cube with books makes it too heavy to lift safely, whatever the board. For heavy contents, choose a smaller box and use more of them. Our product page also lists a higher minimum order on the largest size, so check it before planning a small order.
Some of our largest box sizes travel on 2-day delivery only. Our shipping policy lists which sizes this applies to and the delivery options for each area.
Other box styles you might consider
Board thickness is only one choice. Box style can matter just as much for small e-commerce parcels:
- Crash lock boxes have a base that locks into place as the box is opened, so only the top needs tape. They suit small products and fast packing benches.
- Royal Mail PIP large letter boxes are 20mm deep, for slim items you want to send in the Large Letter format.
- Die cut boxes fold together without tape for a neat small postal box.
Common buying mistakes
Buying double wall for everything
It feels safe, but it raises the cost of every light, robust order and takes up more storage space. If most of your parcels are soft goods, books or boxed accessories, you are paying for strength you do not use. Keep double wall for the orders that need it.
Using single wall for heavy, dense loads
The opposite mistake causes more complaints. Books, tools, tins and jars packed tightly in a large single wall box concentrate a lot of weight on the base and seams. Either move to double wall, choose a smaller box, or split the order.
Choosing a box that is too big
An oversized box with empty space lets the contents move, so even a strong box will not protect them. Empty space also lets the top panel cave in under load, because there is nothing underneath to support it. Pick the smallest box that leaves room for cushioning, and fill remaining gaps with void fill such as kraft paper.
Relying on the box instead of the packing
Board choice cannot make up for poor packing. Wrap fragile items individually, keep them away from the walls, put cushioning under and on top, and make sure nothing rattles when you shake the closed box gently.
Taping only the centre seam
A single strip along the centre seam is common, but heavier boxes benefit from the H-taping method: one strip along the centre seam and one across each end seam, on both top and bottom. Use a tape wide enough for the box; our packaging tape range includes 48mm and 72mm widths.
Forgetting the postage format
A box choice can push a parcel into a more expensive format. Check your carrier's size and weight limits before standardising on a box, and remember that a heavier double wall box adds weight. Royal Mail's limits are listed in its size and weight guide; other couriers publish their own.
What box construction cannot do on its own
It is worth being clear about the limits of any cardboard box, so expectations are realistic.
- Moisture. Corrugated board weakens when it gets wet. Neither single nor double wall boxes are waterproof. Keep stock off damp floors, and do not rely on a box for contents that must stay dry in heavy rain.
- Very heavy or irregular loads. Machinery parts, sharp-edged metal or items over the weight a person can comfortably lift may need specialist packaging, internal fitments or pallet shipping instead.
- Certified performance. If a contract, regulation or insurer requires a tested box specification, ask for that specification in writing. A product name is not a certificate.
- Bad handling. No box guarantees an item will arrive undamaged. Good packing reduces the risk; it does not remove it.
On disposal, plain corrugated cardboard boxes can usually go in household recycling. Recycle Now's cardboard guidance asks for tape and plastic inserts to be removed first, which is worth mentioning to customers if you include packing notes. Arrangements vary by council.
Questions buyers ask
Is double wall always better than single wall?
No. It is stronger, but it is also heavier, bulkier and dearer. For light, robust parcels on a single journey, single wall is usually the sensible choice. Use double wall where the extra strength prevents damage you would otherwise pay for in breakages and refunds.
Can I use single wall boxes for moving house?
For light items such as bedding, clothing and soft furnishings, yes. For books, kitchenware and anything heavy or fragile, double wall boxes cope much better with lifting, stacking in a van and storage. Keep heavy items in smaller boxes so they stay liftable.
How much weight can a double wall box hold?
It depends on the board grades, the box size, how it is packed and how it is closed. We do not publish a weight rating for our boxes, and you should be cautious of any blanket figure that ignores those factors. If you need a rated box, ask for the tested specification. For everyday use, keep heavy contents in smaller boxes, fill the box so the walls are supported, and H-tape the seams.
Are your box sizes internal or external?
Our single wall listing gives sizes as internal dimensions. Board thickness means the outside of any box is slightly larger than the inside, and double wall board adds more to the outside than single wall. If you are working close to a carrier limit, measure the made-up box before you rely on it.
Which box should I use for the Royal Mail Small Parcel format?
Our single wall 17.7 x 13.7 x 6 inch box (450 x 350 x 160mm) is made to the Small Parcel maximum size published by Royal Mail. The packed parcel must also be within Royal Mail's 2kg Small Parcel weight limit. If it is heavier, it will need a larger format or a different service.
Do I need fragile tape or labels on double wall boxes?
A printed warning does not make a parcel stronger, but it tells handlers what is inside. Many sellers add fragile tape or fragile labels to boxes containing breakables. Treat them as a courtesy to handlers, not as protection.
What is the minimum order?
Our single and double wall boxes are sold per box with a minimum of 5 per size, and the largest double wall size has a higher minimum. The current details are on each product page.
Summary
Use single wall boxes for light, robust parcels that make one journey, and double wall boxes for heavy, fragile, valuable or stacked loads. Decide product by product rather than for the whole business, pick the smallest box that leaves room for cushioning, and seal heavier boxes properly. Then stock the two types in proportion to the orders you actually send.
If you are setting up for the first time, start with a handful of the sizes that match your best-selling products in each board type, track which sizes you use fastest, and reorder from there.
