If you want to convert from Halo hipfire to Apex 1X, then the Apex hipfire from there you need to establish some grounds for conversion.
The default of the calculator for any aim is MDV 0%, which is in fact the same as Apex uses as value 1 if your hipfire FOV is the same between the games.
So to break it down, you first do
Halo hipfire -> Apex 1X - These will in your case not be the same FOV, so you need to do some kind of conversion. Do you keep the same 360 distance? The same tracking speed (MDV 0%), the same flick speed to the end of the screen (MDH 100%)?
Then when converting from Apex 1X to Apex hipfire you have the same issue, how do you convert it? What is your preference?
The calculator is by default set up to match hipfire sensitivity using 360 distance, because in most games you use hipfire to navigate and not aim (there are exceptions!). While ADS and scope are set to MDV 0%, which is the default for games like Apex and CoD where the tracking speed of the crosshair remains the same.
The important part is that unless the FOV is identical, none of these are the same. You need to settle on one method to use that suits you. There is no best method as everyone is different, but MDV 0% is usually the most preferred method for aims.