United Kingdom · Royal Mail
Royal Mail parcel postbox size checker.
Parcel Postboxes have a larger slot than a letter box, but it is not unlimited. Check yours before you walk there.
Quick answer: Royal Mail says Parcel Postboxes accept parcels up to 45 cm long, 35 cm wide and 16 cm deep, and up to 2 kg.
Sources checked October 2026. Not affiliated with Royal Mail, Parcelforce, Evri, DPD or DHL.
Your parcel
Postbox result
Enter the size and weight, then press Check postbox fit.
The Parcel Postbox size limit
Royal Mail’s Parcel Postbox page gives maximum dimensions of 45 cm (length) × 35 cm (width) × 16 cm (depth) and a weight limit of 2 kg. That matches the Small Parcel format in its price guides.
45 cm or 44 cm?
The same Royal Mail page contradicts itself. The main text and the “What size parcels can you drop off?” panel say 45 × 35 × 16 cm, but the FAQ answer to “What is the maximum parcel size allowed?” says 44 × 35 × 16 cm. This tool treats 45 cm as the limit because it appears in the main text and the price guide, and warns you if your longest side is between 44 cm and 45 cm. If you are that close, use a Post Office or another drop-off point instead of risking a jammed slot.
Measure the packed parcel
Padding and bulging tape count. A parcel that is 16 cm deep before you wrap it may be 17 cm after.
Too big?
Over 45 × 35 × 16 cm it is a Medium Parcel (up to 61 × 46 × 46 cm, 20 kg), which needs a Post Office branch, collection or another drop-off option. Use the Royal Mail parcel size checker to see the format.
Sources
- Royal Mail: Parcel Postboxes (retrieved October 2026)
- Royal Mail: Small parcel delivery (retrieved October 2026)
- Royal Mail: Online Prices (Click & Drop), valid from 5 October 2026 (PDF) (retrieved October 2026)
Frequently asked questions
What size parcel fits a Royal Mail Parcel Postbox?
Up to 45 × 35 × 16 cm and 2 kg, according to Royal Mail’s Parcel Postbox page.
Why do I see 44 cm for the postbox length?
Royal Mail’s own FAQ on the Parcel Postbox page says 44 × 35 × 16 cm, while the rest of the page says 45 cm. Treat 44 cm as the safe length.
What is the postbox weight limit?
2 kg, per the Parcel Postbox page.
How many Parcel Postboxes are there?
Royal Mail says there are over 1,400 across the UK, open 24/7, and you can find the nearest by postcode on its locations page.
Can I use a Parcel Postbox for a Medium Parcel?
No. Medium Parcels are larger than the 45 × 35 × 16 cm limit.
A guide, not a quote
This page compares your measurements with limits the carriers publish. It does not query any carrier, cannot confirm acceptance or price, and collects no personal data. Carriers change limits and prices, so confirm with the carrier before you ship.