*See also- Modern Scholars on the Casualty Rates for Participants of the First Crusade
Provided below are various death estimates for the crusades to the east roughly covering the period from 1095 to 1291. The extreme range of figures, from one million to nine million, suggests the futility of trying to pin down such a figure with any precision. Modern historians of the crusades tend not to make or trust such estimates, as they are skeptical of the ability of anyone to count the deaths of participants over such long periods of time (nearly 200 years) with any precision and weary of the methodological problems this entails. Nevertheless, such figures are often cited by the media or online and these are likely their sources (presented from lowest to highest).
John Shertzer Hittell– Estimates 1,000,000 total dead for the crusades to the East covering the period from 1095 to 1291.
“In the two centuries of this warfare one million persons had been slain, but it had not been without some compensations.” John Shertzer Hittell, A Brief History of Culture (1874), p.137.
Fredric Wertham– Estimates 1,000,000 total dead for the crusades.
“Many extensive massacres and exterminations have occurred in the past: the Crusades (a million victims); ….” Fredric Wertham, A Sign for Cain: An Exploration of Human Violence (1966), p. 140.
Charles Mackay- Estimates 2,000,000 dead Europeans for the crusades to the East covering the period from 1095 to 1291.
“Now what was the grand result of all these struggles? Europe expended millions of her treasures, and the blood of two million of her children.” Charles Mackay, Memoirs of Extraordinary Popular Delusions and the Madness of Crowds Vol. 2 (1841), p. 100.
Matthew White– Estimates 3,000,000 total dead for the crusades to the East covering the period from 1095 to 1291.
“Estimates of the number of people killed in the Crusades begin at 1 million (Wertham…) and go as high as 9 million (Robertson…) passing through 3 million (Garrison…) and 5 million (Elson…) along the way. I took the low middle (Garrison’s estimate) as my estimate. The geometric means of the extremes is 3 million.” Matthew White, The Great Big Book of Horrible Things: The Definitive Chronicle of History’s 100 Worst Atrocities (2012), p. 576 (see f.n. 1 under The Crusades).
Fielding Hudson Garrison– Estimates 3,000,000 total dead for the crusades to the East covering the period from 1095 to 1291.
“The crusades occasioned the destruction of three million (two million Europeans) in 194 years.” Fielding Hudson Garrison, Notes on the History of Military Medicine (1922), p. 106.
Henry William Elson– Estimates 5,000,000 total dead for the crusades to the East covering the period from 1095 to 1291.
“It is estimated that five million people lost their lives in the crusades.” Henry William Elson, Modern Times and the Living Past (1921), p. 261.
John M. Robertson– Estimates 9,000,000 total dead for the crusades to the East covering the period from 1095 to 1291.
“It is a reasonable calculation that in the two centuries from the first crusade to the fall of Acre (1291) there had perished, in the attempts to recover and hold the Holy Land, nine millions of human beings, at least half of them Christians. Misery and chronic pestilence had slain most; but the mere carnage had been stupendous.” John M. Robertson, A Short History of Christianity (1902), p. 278.
 Many modern scholarly historians have, however, provided death or casualty estimates for individual crusades or battles of the crusades.