World War 1 was one of the bloodiest wars in all of human history. The number of WW1 causalities varies depending on the source you consult but the following statistics are generally regarded as an accurate representation of ww1 death and casualties.
Both Military and Civilian
Deaths: 16.5 million
Wounded: 20 million
Total WW1 Casualties: 35 million +
Deaths: 9.7 million
Wounded: 21.2 million
Prisoners of War and Missing Soldiers: 7.5 million
Deaths as a result of direct military action: 950,000
Deaths caused by disease and famine: 6 million
Country with the most military deaths: Germany (2.1 million)
Country with highest total death toll: Russia (3.8 million)
Highest Percentage of population killed: Serbia (16.11%)
250,000 British Soldiers were suffered a partial or full amputation as a result of fighting in the First World War.