Letterbox package, small or medium parcel? How to choose the right box
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by Verpakkingdeals.nl
6 min reading time
The height of your box often determines which tariff class your shipment falls into. We list the maximum dimensions per package type alongside the actual box sizes you can order.
You have two orders on your packing table. Almost identical contents, almost identical weight — yet you pay more than double the shipping costs for one compared to the other. The difference usually isn't in what's inside, but in the box surrounding it. A few millimeters too thick, and your shipment shifts from a letterbox package to a parcel. That's the most expensive centimeter in your entire process.
Carriers categorize shipments based on dimensions and weight. Those who know these categories and align their boxes accordingly will consistently save money. Below, we list the classifications alongside the box sizes you can actually order.
The four PostNL classes, in numbers
PostNL publishes the maximum dimensions and weights per shipment type on its customer service page. For private shipments within the Netherlands, this looks like:
Shipment type
Maximum dimensions
Maximum weight
Letterbox package
38 × 26.5 × 3.2 cm
2 kg
Small parcel
38 × 28 × 15 cm
3 kg
Medium parcel
100 × 50 × 50 cm
10 kg
Large parcel
176 × 78 × 58 cm
23 kg
These figures are from PostNL's Maximum dimensions and weight of a parcel page. Two caveats: stricter limits apply for international shipments (a letterbox package abroad may weigh a maximum of 1 kg, for example), and if you have a business contract, conditions and rates may differ. Always check the current status with your carrier before purchasing a large stock. If you ship with another party, different limits apply — the principle remains the same.
The 3.2 centimeters that make all the difference
The most important threshold is the height of the letterbox package: 3.2 cm. Anything exceeding that becomes a parcel. This makes the height of your box much more critical than its length and width, as you have ample margin in length and width (38 × 26.5 cm is substantial), while you have virtually no room to spare in height.
Practically, this means: choose a box that is already below 3.2 cm in height, and ensure the contents do not push it over that limit. These two letterbox boxes are well below that:
Note that 2.8 cm is the external dimension. The space you have inside is slightly less, and a thick label or a bulging side will count when the box goes through the measuring template. So never fill a letterbox box to the brim.
What if it really can't be flat
Some products are simply too tall. Then the question is no longer "how do I stay under 3.2 cm," but "how do I stay within the smallest parcel class that still fits." A small parcel with PostNL can be 38 × 28 × 15 cm — that's surprisingly a lot of space, and many webshops pack their items unnecessarily larger than needed.
From our assortment, these boxes fall well within that size:
Unsure between two sizes? Measure your product including the standard padding you use. A box that fits on paper but bulges in practice will still be rejected by the measuring template.
Padding without losing height
In a letterbox package, every millimeter of padding is one you take away from your product. Therefore, use thin material and fill primarily around, not above. For fragile items, you can use a single layer of bubble wrap and fill the remaining space on the sides.
Closing and sealing without making the box thicker
A final pitfall: the finishing. Three layers of tape on top of each other will add a few millimeters exactly where the measuring template passes. One neat strip over the seam is enough, and use a dispenser so you're not tempted to keep taping.
Suppose you make a hundred shipments per month, and for twenty of them, you unnecessarily end up in the parcel class because your box is 4 cm high instead of 2.8 cm. The difference between a letterbox rate and a parcel rate is a few euros per shipment with most carriers. Calculate for yourself what that amounts to over a year — the cost of a different box pales in comparison.
The practical step: take your three best-selling items, measure them including padding, and see which class they currently fall into. If one is just above a limit, you immediately know where your profit lies.
Get started
Want to review your box sizes? Start with letterbox packaging if your shipments can be flat, check out the boxes for anything with volume, and supplement from packaging & shipping for tape, film, and seals. Unsure which size fits your product, or want to know the cost of a larger bundle? Email your dimensions to info@verpakkingdeals.nl and we'll help you figure it out.
Source for dimensions and weights: PostNL, 'Maximum dimensions and weight of a parcel' (postnl.nl). Rates and conditions may change; check current data with your carrier.
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