In total in the years 1940-1945 the Germans registered 400,000 prisoners in Auschwitz (ethnic origins of the prisoners). Data about prisoners incarcerated in the camp in subsequent periods come from reports by the camp resistance movement, reports on the number of prisoners in different parts of the camp and in the camp hospitals as well as from German radio transmissions intercepted by British intelligence and deciphered with Enigma machines. In 1940, there were about 6,000 prisoners in Auschwitz. In mid-1944, there were 17,000 men in Auschwitz I, 47,500 men and women in Birkenau, 9,200 men in Monowitz as well as 17,200 men and women in sub-camps. These figures do not include tens of thousands of Jewish men and women incarcerated in transit camps in Birkenau (mainly BII c and BIII).

(Mini dictionary of terms from the history of Auschwitz)