Cutting Postage Costs on UK Parcels

How do UK carriers price a parcel?

Most UK carriers sort parcels into bands. Each band has a limit for length, width, height and weight. The price is set by the band your parcel falls into, not by its exact size.

That means a parcel just over a limit costs the same as one at the top of the next band. A few millimetres of height or a few grams of weight can push you into a dearer price.

Each carrier sets its own bands and limits, and they change from time to time. Check your carrier's current size and weight rules, then shape your packaging around them.

Write the limits down for the two or three services you use most. Keep the list where you pack, because the person choosing the box is the one who decides the postage.

What is volumetric weight?

Many services charge on whichever is greater: the actual weight or the volumetric weight. Volumetric weight turns the size of the box into a notional weight, so large, light parcels still pay for the space they take up.

A common formula is length × width × height in centimetres, divided by 5,000. Some services use 4,000 or 6,000 instead, so check which divisor yours uses.

Using the 5,000 divisor, a box of 40 × 30 × 30 cm has a volumetric weight of 7.2 kg. If the goods inside weigh 2 kg, you may be charged for 7.2 kg. Cut the box to 30 × 25 × 20 cm and the volumetric weight drops to 3 kg.

Volumetric weight mostly matters for courier services and larger parcels. For small, dense items such as jars or books, the actual weight is usually the higher figure.

Why a smaller box usually saves the most

Box size is the single biggest lever on postage. A box that fits the goods closely keeps you in a lower size band and a lower volumetric weight.

It also saves on filler, packing time and storage space. Every centimetre of air in a parcel is something you pay for twice: once in filler and once in postage.

If your current boxes are standard sizes picked from a catalogue, there is often room to cut. A box made to your product, rather than the nearest stock size, can drop a whole band. Our ecommerce shipping boxes made to size are built for that.

Height is often the costly side

Many services have a cheaper band for flat items under a set thickness, often around 25 mm. Thin parcels such as books, prints and clothing can often fit under it if the packaging is slim.

Above that, the next limits are usually about overall size. Even then, a lower height helps the parcel fit within the length and width limits of a smaller band.

Flat, low boxes are the answer for slim goods. A paperback in a 240 × 170 × 25 mm inside box, for example, may fit a much cheaper band than the same book in a deeper carton. Our slim literature mailers for flat items keep the height down.

Cutting the weight of your packaging

Packaging weight counts towards the parcel weight. On light orders, the box and filler can be a large share of the total.

Choose the thinnest board that still protects the goods. E flute at about 1.5 mm is much lighter than BC double wall at about 7 mm. Use double wall only where the contents or the journey need it.

Swap heavy filler for lighter options, or design the box so no filler is needed. For soft goods, a paper mailing bag often weighs far less than any box. Our kraft paper mailing bags suit clothing and other items that do not crush.

Weigh an empty box on a kitchen scale. A medium box in single wall might weigh a couple of hundred grams, and the same box in double wall noticeably more. Over a thousand parcels, those grams decide whether many orders sit under a weight limit or just above it.

Box or bag: which posts for less?

A bag is lighter and flatter than a box, so it usually costs less to post. It suits goods that cannot be crushed or broken, such as clothing, textiles and some books.

A box gives shape and protection. It suits anything fragile, anything that must arrive looking perfect, and anything sent as a gift.

Padded paper mailers sit between the two. They add a thin cushioning layer without the bulk of a box. Our paper padded envelopes for small items suit accessories, cosmetics and small electronics.

Mixing formats is fine. Many shops send clothing in bags and gifts in boxes, choosing per order rather than forcing everything into one style.

Common mistakes that raise postage

The most common mistake is using one large box size for everything. It is simple to stock, but it charges small orders for space they do not use.

Another is ignoring volumetric weight. A big, light box can cost more than a small, heavy one. Always work out both weights before choosing a box.

The last is forgetting the outside size. Boxes are made to inside sizes, and thick board adds to the outside. Our guide to inside and outside box measurements shows how to allow for it.

One more: changing boxes without telling the packing team. Put the new sizes and the products they hold on a sheet by the bench, so the savings actually reach every parcel.

A worked example: one product, two boxes

Take a candle in a glass jar, 90 mm across and 100 mm tall, weighing 450 g. Packed in a 200 × 200 × 200 mm stock box with paper filler, the parcel weighs about 750 g. Its volumetric weight is 1.6 kg at the 5,000 divisor.

Now pack the same candle in a made-to-size box of 120 × 120 × 130 mm inside, with a simple corrugated insert instead of filler. The parcel weighs around 600 g and the volumetric weight falls to about 0.4 kg.

The smaller box is lighter, takes less room in the van and may fit a lower size band. It also looks neater when it is opened. Our cube cardboard boxes for candles and mugs are a common choice for this kind of product.

Run the same sums on your own best sellers. Even a modest saving per parcel quickly covers the cost of a new box size.