Enter your item's dimensions to check if it will fit through a standard UK letterbox slot.
If your item fits through a UK letterbox, the courier can deliver it directly through the slot without leaving a card or requiring a signature. This increases successful delivery rates and reduces redelivery attempts, which is better for your customers and your reputation as a seller.
Royal Mail will attempt letterbox delivery for items in Large Letter format if they're up to 25mm thick. However, items up to 30-38mm often fit residential letterboxes too, though delivery isn't guaranteed through the slot.
The critical measurement is the height of the letterbox slot (typically 38mm minimum, per BS EN 13724 standards). Your item must be able to slide through this 38mm gap.
Borderline items are risky. Some letterboxes will accept them, others won't. The courier may leave a card instead. For important items, opt for a tracked service or ensure the recipient is home to collect in person.
Yes. Older British letterboxes may be slightly tighter or have smaller slots than modern ones. The 38mm standard is the minimum per BS EN 13724, but some older boxes may only be 30-35mm tall. This is why we recommend staying under 30mm for certainty.
Commercial mailboxes vary widely. Some are much larger slots, others are smaller for security. Always err on the side of caution with business addresses.
You can use a tracked service (e.g., Royal Mail Special Delivery, ParcelForce 24, DPD) where the courier holds it for collection or requires a signature. This costs more but guarantees safe delivery.
This tool uses UK standard letterbox dimensions (BS EN 13724). However, individual letterboxes vary due to age, condition, and custom installations. Always measure your packaged item and consider the flexibility of your packaging material.