Answer:
Due to the impossibility of keeping exact records during World War 2, the death toll is not exact. It is considered that between 60 to 72 million people died during World War 2 from battle injuries, world wide sicknesses, dehydration, starvation, tropical illnesses, murder, genocide (holocaust of Jews and other nationalities and people groups), killing of military prisoners and civilian prisoners and other diseases like typhus, berry berry, vitamin and mineral deficiencies and untreated infections.
They did not have the computer systems we have today and many people were not registered on national census records nor did they have birth or death certificates. Thousands of people were "blown up" and there were no way to determine who had been killed in explosions. So the death told is still an estimate.