My pure's stats were CB 23, hp 24, magic 36 and I trained a bit of magic. With 37 magic and 24 hp the cb was 24. Your so called "100% accurated" combat calculator did not know my combat level. I hope the number help you to make it better.

Did you enter all the fields? That's probably your problem-you missed a field. Also, your problem may be that your magic level gained you a combat level without your noticing.

Mine is off as well. I have Att 76 Str 76 Def 76 HP 77 Mag 74 Ran 61 and Pra 60 and only CB 94. The calculator says I have CB 95.

I've entered those stats into the calculator myself and they came out OK. As others have said, did you fill in all levels correctly?