Here you will find detailed information including sizes and costs for sending standard letters and large letters with Royal Mail.
Royal Mail Size & Weight Guide For Letters
| Max Weight | Max Length | Max Width | Max Thickness | |
|---|---|---|---|---|
| Letter | 100g | 24cm | 16.5cm | 5mm |
| Large Letter | 750g | 35.3cm | 25cm | 2.5cm |
Letters
An estimate would be between 8-12 inches wide and maybe 5.5cm high (or smaller). Width: In old areas, it can be as little as 8 inches wide. But in the newest areas it may be around 12 inches wide. And areas between old and new may vary between these sizes. Download the Royal Mail App to find a Parcel Postbox near you or check this page regularly to keep up to date with the latest locations. The maximum Parcel size allowed into our new Postboxes is 44cm x 35cm x 16cm. Styles and usage. A 'letter box', or 'mail slot' in American and Canadian usage, is a slot, usually horizontal but sometimes vertical, about 30 cm by 5 cm (12 inches by 2 inches), cut through the middle or lower half of a front door.
Ideal for mailing greeting cards, regular letters and postcards, the maximum size that would fall under a 'letter' is 165 mm x 240 mm. We would recommend using an envelope no larger than C5 to fit these restrictions comfortably and avoid any excess costs. The envelope and contents must also weigh under 100g.
Recommended envelope sizes
Cost for sending a letter
| Service | Price |
|---|---|
| 1st Class | 76p |
| 2nd Class | 65p |
Large Letters
For mailing contents such as A4 sized documents, DVDs, certificates, large greeting cards and magazines you would need to send as a large letter. The maximum size is 250 mm x 353 mm and and a maximum weight of 750g so a C4 envelope is a good choice.
Royal Mail Post Box Slot Size
Recommended envelope sizes for a large letter
Cost for sending a large letter
| Weight | 1st Class | 2nd Class |
|---|---|---|
| up to 100g | £1.15 | 88p |
| 101g to 250g | £1.64 | £1.40 |
| 251g to 500g | £2.14 | £1.83 |
| 501g to 750g | £2.95 | £2.48 |
| older postbox ; smaller slot |
The biggest slots are pobably in new areas and also at the local main post office.
Royal Mail Slot Size Chart
Note : The slot slopes upwards
The slot tends to slope upwards (e.g. to keep out rain I guess), so if tight, it could be worth trying to push the parcel in slightly upwards (to follow the angle).
Can you put parcels in postboxes :
My understanding is YES. I have put parcels in.
Estimate sizes :
An estimate would be between 8-12 inches wide and maybe 5.5cm high (or smaller).
Width : In old areas, it can be as little as 8 inches wide. But in the newest areas it may be around 12 inches wide. And areas between old and new may vary between these sizes. This rule probably applies to height as well.
Height
Royal Mail Slot Sizes
: As mentioned above, the newer the postbox the more likely it has more height. My local postbox made around 1981 is probably around 5.5cm high.I use a postbox probably built around 1981 which has a bigger slot than older versions (both in width and height)
Examples for 1980's postbox slot :Using a circa 1981 postbox, I have found the following :
| UK postbox slot (1981) | width | height |
| 20 cm : fits easily 25 cm : fits quite easily large letter size (exactly) : should fit 1980+ slot easy | 4.8cm high package : fits easily 6 cm high box : does not fit |