How do you calculate woven shirts fabric consumption?

If we see in measurement chart, for size-"L" 

1. Center back (CB) lenth is 74 cm,
 2. I.E, 74/2.54 inch = 29.13 inc,
3. Sleeve length is 68 cm,
4. I.E, 68/2.54 inch = 26.77 inch,
5. Chest measurement is 58*2 cm = 116 cm,
6. I.E, 1/2 chest is 116/2 = 58 cm. I.E, 58/2.54 inch = 22.84 inch,
Per pc consumption formula is :
(Back length+Sleeve length + 6) * (1/2 chest + 4 ) * 2 / Fabric width * 36 ( in yards )
(Back length+Sleeve length + 6) * (1/2 chest + 4 ) * 2 / Fabric width * 39.37008 ( in meters )
= ( 29.13+26.77+6 ) x ( 22.84+4 ) x 2 / 60 /39.007 =