Choosing the right box size: seven rules of thumb

Choosing the right box size seems simple, but this is where it most often goes wrong in practice. A box that is too large costs you cooling duration and shipping costs at the same time.

Why too large is worse than too small

Air in a box is space in which heat circulates. A half-full box warms up noticeably faster than a full box of the same size. In addition, with parcel transport you pay for volume that you do not use.

Work from your product

Measure your product including any outer packaging, add the space for coolants, and then look for the smallest box that fits. Not the other way round.

Do not forget the coolants

Gel packs take up space. A 400-gram pack measures about 12 by 21 centimetres. If you do not allow for them, you will be one size short when packing.

Inner versus outer dimensions

With an insulated box, the difference between outer and inner dimensions is considerable, because the wall is thick. A box of 300 by 200 outer dimensions with a 30 millimetre wall has only 240 by 140 of internal space left. Always calculate with the inner dimensions.

Thin or thick

A thick wall insulates roughly two to three times as long, but costs internal space at the same outer dimensions. For short routes a thin wall is often enough; for 24 hours and longer, choose a thick wall.

Standardise

Work with two or three fixed sizes instead of ten. That saves storage space, makes packing faster and gives you better volume pricing.

Fill remaining space

If space is still left over, fill it with packing material. That is cheaper than losing cooling duration.

Step by step: how to arrive at the right size in five steps

1. Measure your product in length, width and height, including the inner packaging it comes in.
2. Determine how much coolant you need. That depends on the transit time, the outside temperature and the required product temperature. You can read how to calculate this in how many gel packs do you need per shipment.
3. Add product and coolant together and leave a few millimetres of play for packing.
4. Look for the smallest inner size that fits this total. Check the inner dimensions per box in the product description, not the outer dimensions.
5. Test with a real shipment. Pack the box the way your team does every day and check that everything fits without forcing.

Common pitfalls

• Measuring without packaging. A product may fit in the box, but the cardboard sleeve around it may not.
• Choosing on litre capacity alone. Two boxes with the same capacity can have a very different shape. A long, flat product will not fit in a nearly cube-shaped box.
• No room for cooling elements underneath and on top. Coolant works best when it surrounds the product from several sides. That costs extra height.
• Choosing one size for the heaviest product. If you have a wide range, first look at which size covers the most orders.
• Forgetting the pallet and the outer carton. The outer dimensions determine how many boxes fit on a pallet. Look at that beforehand, not only at the first delivery.

How do you find the right size in our range?

Our range of EPS boxes runs from 4.7 to 173 litres. Every product page states the inner dimensions. If you are looking for the larger sizes, the overview large EPS box: 28 to 173 litres helps. It sets inner dimensions, wall thickness and quantity per pallet side by side.

An EPS box is supplied with a matching lid as standard. Separate lids are available on request. Our EPS boxes come from our own production since 1972.

Checklist before you order

• Have the inner dimensions been measured with the product, inner packaging and coolant?
• Is the wall thickness matched to the duration of the route?
• Is there little to no empty space left in the filled box?
• Does the filled box fit in your outer carton and on your pallet?
• Have you tested the box with a data logger? A data logger shows how the temperature really behaves.

Frequently asked questions

What if my product falls exactly between two sizes?

In principle, choose the smaller size, if the product still fits neatly with the coolant. If it does not, take the larger size and fill the remaining space. In doubt, send us the dimensions of your product. We will help you think it through.

Does the shape of the box affect the cooling duration?

Yes, but the actual holding time depends on the outside temperature, the fill and the cooling elements. A well-filled box with enough coolant does more than a nice size with a lot of air in it. You can read more about cooling duration in how long does a polystyrene foam box stay cold.

How many different sizes do I need?

For most companies, two to three sizes are enough. Start with the size that covers your best-selling order and only add a size when it demonstrably saves shipping costs or cooling loss.

Can I order cooling elements separately?

Yes. Among our cooling elements you will find gel packs and rigid elements in several sizes.

In summary

Choose the smallest box in which product and coolant fit neatly. Calculate with the inner dimensions, test with a real shipment and work with a small number of fixed sizes. If you order before 14:00, we ship the same day.