A button with a circumference of 7.38 cm will need a buttonhole with the size of 2.35 cm.
Since the circumference is equivalent to 7.38 cm, the formula can be displayed as follows:
7.38 cm = 2πr
r = 7.38cm/2π
r= 1.1751592 cm
diameter = 2r
= 2.3503184 cm or approximately 2.35 cm