The papers will be the first UK nationals to publish in the 315x470mm format, which is used by papers including France's Le Monde, Italy's
La Repubblica and non-UK editions of the Financial Times.
Carolyn McCall, Guardian Newspapers (GNL) chief executive, described the switch as "one of the most important decisions in the 184-year history of The Guardian, and the 213-year history of The Observer".
The titles will be printed on two MAN Roland Colorman presses at the Guardian Print Centre (GPC) at Newsfax International in Bow, East London, and a Colorman at Trafford Park Printers in Manchester.
The format switch comes more than a year earlier than GNL first announced, although an earlier launch date had been expected, particularly since print tests began at GPC on 23 May.
More at http://www.printweek.com.
Have your say in the Printweek Poll
Related stories
Latest comments
"Sad to see another print company facing financial trouble. The industry is tough, and this highlights the ongoing challenges many are facing. Hope employees and customers get clarity soon."
"Not surprised, businesses need to prepare for these attacks rather than thinking that they're going to avoid them. At the very least, data needs to be fully protected with air gaps in place..."
"So much for growth then!"
Up next...
Six months after Charlesworth deal
TJ Books looks to appoint admins
Current timeframes are insufficient
Election print and postal pressures highlighted in AEA report
"Significant milestone"
Riso celebrates 20 years of inkjet
Strengthens existing product portfolio