As of September 2014, the price for a Royal Mail Second Class letter stamp is 53 pence. This stamp is valid for letters and postcards up to 100 grams being mailed within the United Kingdom.
According to Royal Mail, a letter may have a maximum length of 240 millimeters and a maximum width of 165 millimeters, and be no more than 5 millimeters thick. A large letter may be no more than 353 millimeters long, 250 millimeters wide, 25 millimeters thick and may weigh no more than 750 grams. Postage for a Second Class large letter ranges from 73 pence to £2.01, depending on weight. All postage prices are exempt from Value Added Tax.