A fat quarter is a quarter yard cut that measures approximately 18" x 21" to 18" x 22" rather than the standard 9" x 44" quarter yard.
Fat Quarter
18 inches x 21 inches = 45 cm x 53 cm
18 inches x 22 inches = 45 cm x 55 cm
If you cut 1/2 yard of fabric, then cut the 1/2 yard on the fold, you've just created 2 fat quarters!