125,000 persons were investigated by the Spanish Inquisition, of which 1.8% were executed.
There were two major Inquisitions, the Medieval Inquisition and Spanish Inquisition. Although there are no exact numbers, scholars believe they have estimated Inquisition deaths reasonably accurately. There were not as many deaths as the popular press claims. Numbers have often been inflated to as high as 9 million by the popular press, with absolutely no scholarly research. This figure is completely erroneous. A broad range of scholars, many of whom were not Catholic, have carefully studied the Inquisitions. They looked at all the existing records and were able to extrapolate. In the Medieval Inquisition, Bernard Gui was one of the most notorious of the medieval inquisitors. (so much so that the sick modern pornography industry has turned him into a hero). He tried 930 people out of which 42 were executed (4.5%). Another famous Inquisitor was Jacques Fournier who tried 114 cases of which 5 were executed (4.3%). Using numbers that are known, scholars have been able to surmise that approximately 2,000 people died in the Medieval Inquisition. (1231-1400 AD)
According to public news reports the book's editor, Prof. Agostino Borromeo, stated that about 125,000 persons were investigated by the Spanish Inquisition, of which 1.8% were executed (2,250 people). Most of these deaths occurred in the first decade and a half of the Inquisition's 350 year history. In Portugal of the 13,000 tried in the 16th and early 17th century 5.7% were said to have been condemned to death. News articles did not report if Portugal's higher percentage included those sentenced to death in effigy (i.e. an image burnt instead of the actual person). For example, historian Gustav Henningsen reported that statistical tabulations of 50,000 recorded cases tried by nineteen Spanish tribunals between 1540-1700 found 775 people (1.7%) were actually executed while another 700 (1.4%) were sentenced to death in effigy ("El 'banco de datos' del Santo Oficio: Las relaciones de causas de la Inquisición española, 1550-1700", BRAH, 174, 1977). Jewish historian Steven Katz remarked on the Medieval Inquisition that "in its entirety, the thirteenth and fourteenth century Inquisition put very few people to death and sent few people to prison; 90 percent of its sentences were canonical penances" (The Holocaust in Historical Context, 1994).
During the high point of the Spanish Inquisition from 1478-1530 AD, scholars found that approximately 1,500-2,000 people were found guilty. From that point forward, there are exact records available of all "guilty" sentences which amounted to 775 executions. In the full 200 years of the Spanish Inquisition, less than 1% of the population had any contact with it, people outside of the major cities didn't even know about it. The Inquisition was not applied to Jews or Moslems, unless they were baptised as Christians.
If we add the figures, we find that the entire Inquisition of 500 years, caused about 6,000 deaths. These atrocities are completely inexcusable. These numbers are however, a far cry from the those used in the popular press by people who are always looking to destroy the Church. This is about equal to the number of war related deaths that have occurred in Afghanistan and Iraq in the 2 years since the US responded to 9/11.
Another thing to note is that the Spanish Inquisition, in a wrong way, may have saved some lives. In many European countries in the 16th century, religious wars were the cause of tens of thousands of deaths. But in Spain, there was political and religious unity as a result of the Inquisition, and there was no such war.