grate question

fire grates come in sizes that are the arc length of the front edge

a manufacturer provides these dimensions for a '16 inch' grate:

assume that the centre of the arc is at the back edge of the grate:

calculate the length of the front arc in mm

convert to inches using 25.4 mm = 1 inch

is the arc length close to 16" ?


the dimensions for other grate sizes are:
12" = 280mm, 220mm, 170mm
14" = 330mm, 240mm, 210mm
what are the arc lengths of these grates?