*See also- Death Estimates for the Crusades
Provided below are various casualty estimates given by modern scholars for the participants of the First Crusade.
Jean Flori– 66% overall casualty rate for crusaders during the First Crusade.
“Tous ces facteurs doivent nous inciter à ne pas minimiser outre mesure l’ampleur des pertes subies. Les chroniqueurs, dans leur ensemble, évaluent les effectifs parvenus à Jérusalem à environ 10% des croisés présents à Constantinople. C’est probablement excessif, et l’on peut, là encore, accorder une marge d’incertitude de 1 à 3.”
Jean Flori, Pierre L’Ermite, p. 453.
John France– 75% overall death rate for crusaders during the First Crusade.
“In the light of all that they had gone through and all the attritions they had faced an overall loss rate of 3:1 would appear reasonable. That would have fallen rather more heavily on the followers than on the knights and lords; they might have been more at risk in battle but battle losses were only a fraction of total losses and their superior wealth must have meant they were less exposed, though never immune, to malnutrition and its attendant risks.” John France, Victory in the East, p. 142.
Jonathan Riley-Smith– 37.3% overall death rate for crusaders during the First Crusade.
“So of 217 (or 230) individuals, 37.3% (or 35.2%) died, a mortality which turns out to be not so very different from Powell’s for the Fifth Crusade. In place of France’s three-quarters and Flori’s two-thirds dead, I am left with rather more than one-third, although we simply do not know what conditions were like among the knights’ supporters- grooms, squires and the rest- whom France rightly includes among the fighting element, let alone among the poor.” Riley-Smith, “Casualties and Knights on the First Crusade,” Crusades 1 (2002), p. 17-18.
Christopher Tyerman– 33% of aristocrats died on the First Crusade, with higher attrition rates for others, possibly as high as 70 or 80%.
“Of the aristocrats, it has been calculated that probably over a third died or were killed on each major campaign, and of the lesser crusaders, the attrition was probably much higher. Some people calculate it as much as 70 or 80 percent.” See NPR Interview-Interview: Christopher Tyerman Discusses His Book on the Crusades, https://www.npr.org/programs/wesun/transcripts/2005/feb/050227.tyerman.html (accessed Jan. 30, 2019)
Peter Frankopan– 66% reduction of the crusader army by the time it reached Jerusalem.
“Moreover, while it was still substantial, the attacking army had decreased dramatically in size over the course of the previous two years, losing men in battle as well as to illness and disease. [Citing John France] It has been estimated that by time it reached Jerusalem, the western army had been reduced to a third of its original strength.” Peter Frankopan, The First Crusade: The Call from the East, p. 173-174.
* I will update and add new figures by other scholars as I come across them.