I was just doing some updating on my CPL and thought maybe some of you could possibly use this info:

cost of fuel per kg =C(f)
time related cost per minute of flight C(t)
Fixed cost Independant of time C(c)
Trip Fuel C(tf)
Trip time C(tt)

CI=Cost Index

CI= C(f)xC(tf)+C(t)xC(tt)+C(c)

So now you know how to calculate approx as close as possible anyway to get the CI that is requested when filling out your CDU on preflight.

Just a little bit of info.

Safe flights