One of the areas most mistakes with this happen are around chamber volume and down fill volume. Many simple step calculators just use published figures from piston and head manufacturers and should be fairly repeatable if you use the right figures. That isn't to say they will all be exact, but they should be within a narrow range of each other.

One I like to use for static figures is here: https://www.rbracing-rsr.com/compstaticcalc.html

Once you have accurate static numbers, I use this one to account for cam, altitude, and boost variations to figure out what needs to change for pump gas livability: https://rbracing-rsr.com/comprAdvHD.htm