• Royal Mail Slot Size Chart
• Royal Mail Post Box Slot Size
• Royal Mail Slot Sizes

Here you will find detailed information including sizes and costs for sending standard letters and large letters with Royal Mail.

• The European standard for letter boxes, EN “Postal services – Apertures of private letter boxes and letter plates – Requirements and test methods” specifies among other things: that envelope size C4 (229 mm × 324 mm) must be deliverable without bending or damage; that the internal volume must able to hold at least a 40 mm.
• Need to post a heavy or large parcel, or both? Take a look at our parcel weight and size restrictions for our international services and mail formats.

Royal Mail Size & Weight Guide For Letters

Large letters must again pass through without getting stuck and goes up to 25mm in thickness. If your mail does not fit either slot it is then becomes a small or large parcel. Small parcel is items to be posted up to the size of 2 kg in weight, 35cm in length, 25cm in width and 16cm in length. Any thing bigger is a Large Parcel. The maximum size is 250 mm x 353 mm and and a maximum weight of 750g so a C4 envelope is a good choice. Recommended envelope sizes for a large letter C4 Envelopes. How strict are the Royal Mail with letter / parcel sizes? This is always a source of concern for me, I have recently sold a chunk of stuff through ebay and it is difficult to get to a post office. You can do postage through ebay but there are times when it is debatable if it is a large letter or a parcel.

Letters

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

Large Letters

Royal Mail Slot Size Chart

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.

Recommended envelope sizes for a large letter

Royal Mail Post Box Slot Size

Cost for sending a large letter

Royal Mail Slot Sizes