Hi! The calculations for BF4 are 100% accurate, I've checked them many times In your case two things might cause the difference in distance. First of all, is raw mouse input turned on? If yes, then the cause is most likely inaccuracy in the mouse sensor. It's not uncommon that they are 10% off, meaning when you have set it to 800 DPI, it is in reality 720 DPI. To doublecheck, try to calculate another game in the calculator if you have one, preferably one with no acceleration (like Mincraft, Crysis 3, BF3, TF2), and see if the distance is still 10% off.