letter-size
adjective [ before noun ]
US ukus(also letter) COMMUNICATIONS, WORKPLACE, MEASURES
used to describe paper that measures 8½ inches by 11 inches (= 21.59 cm by 27.94 cm), the standard size of office paper in the US:
I reformatted my document to print it on letter-size paper.
The calendars will be printed on US letter paper.
Compare
A4