Which letterbox box do you need? A6, A5+, and A4 sizes explained
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by Verpakkingdeals.nl
6 min reading time
PostNL and DHL use 38 x 26.5 x 3.2 cm and 2 kg as the limit for a letterbox package. In this guide, you can read about the relationship between A6, A5+, and A4 sizes, which sizes we stock ourselves, what a box costs you per shipment, and which packaging materials you need for it.
One millimeter too thick and you're suddenly paying the parcel rate. For webshops, Vinted sellers, and self-employed individuals who ship many small items, the letterbox box is the difference between profit and loss on shipping costs. In this article, we list the official dimensions, explain which size to choose when, and calculate what a box truly costs you.
Official dimensions: what do you need to comply with?
Both PostNL and DHL in the Netherlands apply the same strict limit for a letterbox parcel:
Maximum 38 x 26.5 x 3.2 cm
Maximum 2 kg
Are you shipping internationally via PostNL? Then the requirements are stricter: maximum 38 x 26 x 3.2 cm and 1 kg.
The trickiest number is that 3.2 cm height. Length and width are rarely the problem — thickness is. A box that is neatly 2.8 cm when empty can easily become 3.4 cm after being filled with packing material and a sturdy layer of tape. In that case, your shipment will still fall under the parcel rate, or it won't fit through the letterbox at all.
A6, A5+, or A4: which size do you choose?
In practice, most shippers work with three standard sizes. All three have a height of 28 mm, leaving you with 4 mm of leeway.
Size
Dimensions
Suitable for
A6
180 x 115 x 28 mm
Jewellery, phone cases, cards, cosmetics, small parts, keychains
A5+
255 x 160 x 28 mm
Books, T-shirts, underwear, pins & badges, games, small electronics
A4
299 x 213 x 28 mm
Clothing, multiple items at once, documents with contents, textiles
A6 — the workhorse for small items
Do you sell jewellery, accessories, or small cosmetics? Then A6 is your standard nine times out of ten. The Recycled Letterbox Box A6 (bundle of 100 pieces) costs €17.95, or 18 cents per box. For an average order of €15 to €25, that's negligible on your margin.
A5+ — the most versatile size
Do you sell clothes, books, or multiple small items in one order? The Recycled Letterbox Box A5+ (bundle of 100 pieces) costs €24.00 — 24 cents per box. A folded T-shirt fits perfectly, provided you fold it flat and press it gently.
A4 — when you need to fit a bit more
The A4 size (299 x 213 x 28 mm) is the largest size that still fits through most letterboxes. Handy for textiles or orders with multiple items. Note: the larger the surface, the faster the box will sag when the letterbox is full. So fill it firmly to help the box maintain its shape. We no longer carry this size ourselves; our range goes up to A5+. In the Letterbox Packaging collection, you can see which sizes we do have in stock.
Why recycled cardboard is a smart choice
All the boxes mentioned above are made from recycled cardboard. This is not only better for the environment, but it also works commercially: more and more customers are paying attention to packaging waste, and a brown, unbleached box communicates that without you having to say anything about it. An additional advantage: recycled cardboard is generally cheaper than white bleached cardboard, while the sturdiness is comparable.
What else you need to ship well
A box alone is not enough. These are the four things that make the difference between a package that arrives intact and a return:
Filling material. If the contents move, they will break. For fragile items, use bubble wrap (50 x 500 cm, €5.00); if you ship larger volumes, the large bubble wrap roll of 500 m is much more economical per meter. Do pay attention to your total thickness — one layer of bubble wrap can easily add 3 mm.
Security seals. Do you ship more valuable items? With the VOID security seals (60 pieces, €9.95), you can immediately see if a box has been opened en route. That saves discussion in case of damage claims.
Bubble envelopes as an alternative. For flat, non-breakable items, padded envelopes are often more convenient and lighter than a box. They are available from €0.80 each.
Calculation example: what do packaging costs per shipment?
Suppose you ship jewellery in an A6 box:
A6 box: €0.18
Tape (approx. 30 cm): €0.02
A little bubble wrap: €0.05
Total: approximately €0.25 per shipment
With 200 shipments per month, you would spend €50 on packaging. If you were to ship the same order in a regular box that doesn't fit through the letterbox, you would easily pay a few euros extra in shipping costs per shipment — with 200 shipments, that adds up to hundreds of euros per month. The size of your box is therefore one of the cheapest ways to improve your margin.
Five practical tips
Measure AFTER packing, not before. Lay the filled, taped box flat on the table and measure the highest point.
Fold clothes flat and press them down. A rolled-up shirt is 5 cm thick, a flat-folded shirt is 2 cm.
Buy in bundles. Single boxes are two to three times more expensive per piece than a bundle of 100.
Keep two sizes in stock. With only A6, larger orders will be too expensive to ship; with only A5+, you waste space and filling material.
Test once with an actual letterbox. Older letterboxes sometimes have a narrower slot than the norm. If your box fits through that, it will fit through anywhere.
Get started
Do you know what size you need? Then view the full collection of Letterbox Packaging, or browse all boxes and envelopes on Verpakkingdeals.nl. Are you unsure about the right size for your product? Feel free to email us at info@verpakkingdeals.nl — we are happy to help.
The stated maximum dimensions are based on the current specifications of PostNL and DHL eCommerce. When in doubt, always check the terms and conditions of your carrier, as rates and dimensions may change.
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