According to medieval historian Philip Daileader, it is likely that over four years, 45–50% of the European population died of plague. Norwegian historian Ole Benedictow suggests it could have been as much as 60% of the European population.
In 1348, the disease spread so rapidly that before any physicians or government authorities had time to reflect upon its origins, about a third of the European population had already perished. In crowded cities, it was not uncommon for as much as 50% of the population to die. Half of Paris' population of 100,000 people died. In Italy, the population of Florence was reduced from between 110,000 and 120,000 inhabitants in 1338 down to 50,000 in 1351. At least 60% of the population of Hamburg and Bremen perished, and a similar percentage of Londoners may have died from the disease as well, with a death toll of approximately 62,000 between 1346 and 1353.
Florence's tax records suggest that 80% of the city's population died within four months in 1348. Before 1350, there were about 170,000 settlements in Germany, and this was reduced by nearly 40,000 by 1450. The disease bypassed some areas, with the most isolated areas being less vulnerable to contagion. Plague did not appear in Douai in Flanders until the turn of the 15th century, and the impact was less severe on the populations of Hainaut, Finland, northern Germany, and areas of Poland. Monks, nuns, and priests were especially hard-hit since they cared for victims of the Black Death.