A traditional 1⁄8-yard cut and a fat-eighth cut contain the same amount of fabric, but have different shapes.
A traditional 1⁄8-yard cut is 4-1⁄2" × 44".
A fat eighth is cut crosswise from a 1⁄4-yard piece of fabric, a 9" × 44" rectangle cut in half to make a 9" ×21" fat 1⁄8-yard piece.
If you cut 1/4 yard of fabric, then cut the 1/4 yard on the fold, you've just created 2 fat eighths!
Fat Eighth
9 inches x 21 inches = 22 cm x 53 cm
9 inches x 22 inches = 22 cm x 55 cm