How many people died in the Crusades?

Which crusade? There were several. And do you want figures for both sides?

Actually they're all estimates, nobody was keeping accurate records back in those times. It IS known that several cities had all their inhabitants slaughtered, some of the cities were very large ones.

There were 8 major Crusades over the 11th to 13th centuries with several associated wars in between. In modern estimates the death rate was around 60% or more, though our idea of statistics were not kept in those days.

Death was not always the direct result of war. The First Crusade set out with 35,000 men but only around 12,000 survived to take Jerusalem. They died of disease, starvation, injuries etc. In addition there were the camp followers who cooked, cleaned, looked after the needs of the men, looked after the horses eg blacksmiths, and not many of them survived the trip.

To get reasonable estimates you need to look at details of each individual Crusade and the number of troops and camp followers. Then you have to look at what was happening on the Muslim side and their statistics.

100s of thousands died during the crusades.

Not sure there are any reliable sources.

Not nearly enough.