The total number of military and civilian casualties in World War I is estimated to be 15 to 22 million deaths and about 21 million wounded military personnel, making it one of the deadliest military conflicts in human history.

The total number of deaths includes nine to 11 million military personnel. The civilian death toll was about six to 13 million. The Triple Entente (also known as the Allies) lost about six million military personnel while the Central Powers lost about four million. At least two million died from diseases and six million went missing, presumed dead. This article lists the casualties of the belligerent powers based on official published sources.

About two-thirds of military deaths in World War I were in battle, unlike the conflicts that took place in the 19th century when most deaths were from disease. Nevertheless, disease, including the 1918 flu pandemic and deaths while held as prisoners of war, still caused about one third of total military deaths for all belligerents.

Classification of casualty statistics

Casualty statistics for World War I vary to a great extent; estimates of total deaths range from nine million to over 15 million. Military casualties reported in official sources list deaths due to all causes, including an estimated seven to eight million combat related deaths (killed or died of wounds) and another two to three million military deaths caused by accidents, disease and deaths while prisoners of war. Official government reports listing casualty statistics were published by the United States and Great Britain.Military Casualties – World War – Estimated. Statistics Branch, GS, War Department, 25 February 1924The War Office, Statistics of the Military Effort of the British Empire During the Great War 1914–1920 These secondary sources published during the 1920s, are the source of the statistics in reference works listing casualties in World War I.The European Powers in the First World War: An Encyclopedia Spencer C. Tucker Garland Publishing, New York 1999 John Ellis, The World War I Databook, Aurum Press, 2001, pp. 269–70World War I: People, Politics, and Power, published by Britannica Educational Publishing (2010) p. 219 This article summarizes the casualty statistics published in the official government reports of the United States and Great Britain as well as France, Italy, Belgium, Germany, Austria and Russia. More recently the research of the Commonwealth War Graves Commission (CWGC) has revised the military casualty statistics of the UK and its allies; they include in their listing of military war dead personnel outside of combat theaters and civilians recruited from Africa, the Middle East and China who provided logistical and service support in combat theaters.Figures include identified burials and those commemorated by name on memorials The casualties of these support personnel recruited outside of Europe were previously not included with British war dead, however the casualties of the Labour Corps recruited from the British Isles were included in the rolls of British war dead published in 1921. The methodology used by each nation to record and classify casualties was not uniform, a general caveat regarding casualty figures is that they cannot be considered comparable in all cases. First World War civilian deaths are "hazardous to estimate" according to Micheal Clodfelter who maintains that "the generally accepted figure of noncombatant deaths is 6.5 million."Clodfelter, Micheal (2002). Warfare and Armed Conflicts – A Statistical Reference to Casualty and Other Figures, 1500–2000 2nd Ed.. . p. 479

Casualties by borders of 1914

Nation Population (millions) Combat deaths and missing in action (included in total military deaths) Total military deaths (from all causes) Civilian deaths (military action and crimes against humanity) Increase in civilian deaths (malnutrition and disease excluding Influenza pandemic) Total deaths Deaths as % of population Military wounded Allies and co-belligerents of World War I 5.0 61,527 59,330to 62,149 59,330to 62,149 1.2% to 1.2% 152,171 7.2 56,638 56,639 to 64,996 1,963 58,639 to 66,996 % to % 149,732 315.1 64,449 64,449 to 73,905 64,449 to 73,905 % to % 69,214 1.1 18,166 16,711 to 18,060 16,711 to 18,060 % to % 41,317 0.2 1,204 1,204 to 1,570(included with UK) 1,204to 1,570 % to % 2,314 6.0 7,121 7,121 to 9,726 7,121 to 9,726 % to % 12,029 (and colonies) 45.4 744,000 887,858 16,829Gilbert, Martin (1994). Atlas of World War I. Oxford UP. (908 civilians killed in naval attacks) 107,000Hersch, L., La mortalité causée par la guerre mondiale, Metron- The International Review of Statistics, 1927, Vol 7. pp. 47–61 to 400,000 867,829 to 1,011,687 % to % 1,675,000 380.0 953,104 949,454 to 1,118,264 18,829 107,000 1,077,283to 1,244,093 % to %2,101,077 7.4 38,170 38,170to 58,637Annuaire statistique de la Belgique et du Congo Belge 1915–1919. Bruxelles. 1922 p. 100 Per Annuaire statistique de la Belgique et du Congo Belge 1915–1919 figure of 58,637 includes 2,620 colonial troops and 15,650 porters in Africa 23,700Annuaire statistique de la Belgique et du Congo Belge 1915–1919. Bruxelles. 1922 p. 100 62,000Hersch, L., La mortalité causée par la guerre mondiale, Metron- The International Review of Statistics, 1927, Vol 7. pp. 59–62 123,870to 144,337 % to % 44,686 39.6 1,150,000Huber, Michel (1931). La Population de la France pendant la guerre. Paris. p. 420. The figure includes killed, missing in action and died of wounds excluding died of diseaseOfficial History of the Australian Army Medical Services, 1914–1918 Volume III – Special Problems and Services (1st edition, 1943) p. 870 1,357,000to 1,397,800Huber, Michel (1931). La Population de la France pendant la guerre. Paris p. 414 40,000Ellis, John (1993). World War I–Databook. Aurum Press. , p. 269Randal Grey. Chronicle of World War I, Vol2 Facts on File 1991 p. 292 300,000 to 600,000 1,697,000to 1,737,800 % to % 4,266,000Military Casualties-World War-Estimated," Statistics Branch, GS, War Department, 25 February 1924; cited in World War I: People, Politics, and Power, published by Britannica Educational Publishing (2010) p. 219 4.8 5,000 5,000 to 26,000Urlanis, Boris (1971). Wars and Population. Moscow p. 209 150,000Hersch, L., La mortalité causée par la guerre mondiale, Metron- The International Review of Statistics, 1927, Vol 7. pp. 80–81 155,000 to 176,000 % to % 21,000 35.6 460,000 460,000 to 709,000Mortara, G (1925). La Salute pubblica in Italia durante e dopo la Guerra. New Haven: Yale University Press. pp. 28–29 3,400Mortara, G (1925). La Salute pubblica in Italia durante e dopo la Guerra. New Haven: Yale University Press. pp. 56–57 332,000 to 589,000Hersch, L., La mortalité causée par la guerre mondiale, Metron – The International Review of Statistics, 1927, Vol 7. pp. 52–59 1,052,400 to 1,301,400 % to % 947,000 to 1,050,000 53.6 300 300 to 4,661International Labour Office, Enquête sur la production. Rapport général. Paris [etc.] Berger-Levrault, 1923–25. Tom 4, II Les tués et les disparus p. 29 300 to 4,661 % to % 907 0.5 3,000 3,000 to 13,325 3,000 to 13,325 % to % 10,000 6.0 7,222 7,222 13 82,000Hersch, L., La mortalité causée par la guerre mondiale, Metron- The International Review of Statistics, 1927, Vol 7. pp. 61–64 89,235 % 13,751 7.5 335,706 250,000 to 335,706 130,000Erlikman, Vadim (2004). Poteri narodonaseleniia v XX veke : spravochnik. Moscow. p. 51 . 200,000 580,000 to 665,706 % to % 120,000 175.1 775,369 to 1,700,000 1,700,000 to2,254,369 410,000Erlikman, Vadim (2004). Poteri narodonaseleniia v XX veke : spravochnik. Moscow. p. 18 .(Civilians killed on Eastern Front) 730,000 2,840,000 to3,394,369 % to % 3,749,000 to4,950,000 4.5 127,500 300,000Hersch, L., La mortalité causée par la guerre mondiale, Metron- The International Review of Statistics, 1927, Vol 7. pp. 65–76to 450,000Frédéric Le Moal, La Serbie du martyre à la Victoire 1914–1918, 2008, éditions 14–18 (2013) (), p. 231 450,000to 800,000 750,000 to 1,250,000 % to % 133,148 92.0 53,402 116,708 757 117,466 % 204,002 806.6 4,833,404 5,186,854 to 6,433,692 626,699 3,420,000to 3,770,000 9,235,553 to 10,080,391 % to % 11,611,271 to 12,812,271 Central Powers 51.4 1,016,200Ellis, John (1993). World War I Databook: The Essential Facts and Figures for All the Combatants. London: Aurum Press. . p. 269Österreichisches Bundesministerium für Herreswesen (1938). Österreich-Ungarns letzer Krieg, 1914–1918 Vol. 7. Vienna. VII, Beilage 37 1,200,000to 1,494,200 120,000.Erlikman, Vadim (2004). Poteri narodonaseleniia v XX veke : spravochnik. Moscow. p. 49 .(Civilians killed in the fighting on the Eastern Front) 467,000Grebler, Leo (1940). The Cost of the World War to Germany and Austria-Hungary. Yale University Press. p. 147 1,787,000 to 2,081,200 % to % 3,620,000 4.5 87,500 87,500 100,000Urlanis, Boris (1971). Wars and Population. Moscow p. 268 187,500 % 152,390 64.9 1,800,000The War Office (1922). Statistics of the Military Effort of the British Empire During the Great War 1914–1920. Reprinted by Naval & Military Press p. 355. .Urlanis, Boris (1971). Wars and Population. Moscow p. 85, The demographer Boris Urlanis put total German war dead at 2,037,000, he estimated that the figure included 1,796,000 men killed, dead from wounds and gas poisoning. 2,037,000Heeres-Sanitaetsinspektion im Reichskriegsministeriums (1934) (in German). Sanitaetsbericht über das deutsche Heer, (deutsches Feld- und Besatzungsheer), im Weltkriege 1914–1918. Volume 3, Sec 1. Berlin. pp. 12–14 720The War Office (1922). Statistics of the Military Effort of the British Empire During the Great War 1914–1920. Reprinted by Naval & Military Press. p. 678. .(Civilians killed by Allied bombing) 300,000 to 763,000Vincent, C. Paul (1985). The Politics of Hunger: The Allied Blockade of Germany, 1915–1919. Athens (Ohio) and London: Ohio University Press. 2,198,420 to 2,800,720 % to % 4,215,662 21.3 305,085Ordered to Die: A History of the Ottoman Army in the First World War, Edward J. Erickson. p. 211. 325,000 to 771,844Erickson, Edward J., Ordered to Die: A History of the Ottoman Army in the First World War, Greenwood 2001. p. 211 1,500,000Totten, Samuel, Paul Robert Bartrop, Steven L. Jacobs (eds.) Dictionary of Genocide. Greenwood Publishing Group, 2008, p. 19. . 1,000,000Poteri narodonaseleniia v XX veke : spravochnik. Moscow. . pp. 61, 65, 73, 77–78 (In current borders Turkey 500,000; Syria 160,000; Lebanon 110,000; Iraq 150,000; Israel/Palestine 35,000 and Jordan 20,000) 2,825,000 to 3,271,844 % to % 400,000 to 763,753 142.1 3,208,785 3,386,200 to 4,390,544 1,620,720 1,991,000 to 2,330,000 6,997,920 to 8,341,264 % to % 8,388,052to 8,751,805 Neutral nations 2.8See footnote re: Danes in German military 700 700 % — 0.3 2,800 See footnote 2.4 1,180 1,180 % — 10.5 2,000,000 2,000,000 % — 5.6 800 800 % — 0.7 to 0.870,0008.75% to 10%— 0.0087440.05%— Grand total 959.7 8,042,189 8,573,058 to 10,824,240 2,250,099 5,411,000 to 8,100,000 15,000,000 to 22,000,000 % to % 22,101,100 to 23,665,873 The source of population data is: Haythornthwaite, Philip J., The World War One Source Book pp. 382–383Haythornthwaite, Philip J., The World War One Source Book Arms and Armour, London, 1993, .

Casualties by post-war (1924) borders

The war involved multi-ethnic empires such as Great Britain, France, Germany, Russia, Austria-Hungary and Turkey. Many ethnic groups in these territories were conscripted for military service. The casualties listed by modern borders are also included in the above table of figures for the countries that existed in 1914. The casualty figures by 1924 post war borders are rough estimates by Russian historian Vadim Erlikman in a 2004 handbook of human losses in the 20th century, the sources of his figures were published in the Soviet era and in post-Soviet Russia.Erlikman, Vadim (2004). Poteri narodonaseleniia v XX veke : spravochnik. Moscow. .