When plugging in information......

Most calculators default at 1.5" for bolt action, and 2.6" for sporting

Are they measuring from the center of the barrel to the center of the scope or the top of the barrel to the center of the scope?

I measured from center of barrel to center of scope and I'm right at 3", if I measure from the top of the barrel to the center of the scope I'm right at 2.75"

This is on a MEGA 308 with a 4-14 scope

AccurateShooter Height Above Bore article

Center to center.

Thanks

Much of this information does not have to be perfect because too many other variables make it impossible to accurately predict bullet drop from your rifle.  Punch in 2.7" or 2.8" for your circumstances, do both, the numbers won't change much and they won't reflect exactly what you get on target anyway.

Elevation, atmospheric pressure, ambient temperature, barrel length, bullet selection, actual velocity, ballistic coefficient and probably half a dozen other inputs will effect bullet drop and drift in the real (your) world. These computer programs are designed to get you close enough for government work, final drop numbers on your scope with your rifle and ammo combination need to be recorded for future reference based on your actual findings at known ranges.