The Holocaust lasted from 1941 till 1945 however Jews were being killed in Germany since 1933, so it would be 1933 to 1945 and that makes 12 years. Approximately 5 and 6 millions Jews were killed, 1.5 million were children. But it's impossible to exactly how many Jews were killed since their deaths were in different events such as the concentration camps (ex: Auschwitz)