Royal Mail Letter Sizes

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

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

• DL Envelopes
• C7 Envelopes
• C6 Envelopes
• C5 Envelopes
• 5x7 Envelopes
• 152 x 216 mm Envelopes

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.

Recommended envelope sizes for a large letter

• C4 Envelopes