Number of copies
Two different sources give the following numbers:
- The year 2000 edition of The Complete Wargames Handbook provides figures for the best selling computer games between 1993 and 1999. It puts Doom II as number three, with 1.5 million copies (behind Myst with 4.2 and Microsoft Flight Simulator with 2.8). Doom ends up number 8, with 1.1 million, and Ultimate Doom number 20, at 788,000. 
- A list by now-defunct research firm PC Data for January 1993–April 1998 puts the sales for Doom II at 1,815,882 and Doom at 1,361,943, on positions 3 and 4 .
Based on these data, one may place the sales until 1999 in the range 1.9–2.1+ million for Doom (including Ultimate Doom), and 1.5–1.8+ million for Doom II. It is probably safe to deduce that as of 2005, both Doom and Doom II have sold well over 2 million copies each. (The Page of Doom verifies, though no source is cited for the claim, that Doom II has "2 millions sold to this day" .) Hence, the PC versions of Doom and Doom II have likely sold over 4 million copies combined. The 4 million figure is also given in the CNET article Doom 3: a short history of shooting stuff, August 2, 2004.
This number does not include sales for the console versions of Doom, nor Final Doom, which when added may put the total for the entire original Doom franchise significantly higher. The PlayStation version is part of Sony's "Greatest Hits" collection, which indicates that it has sold over 500,000 copies (IGN, January 9, 2002, ).
Although Myst and Microsoft Flight Simulator have sold more, it must be noted that Doom has been distributed primarily in its free shareware version, which is commonly estimated to have been played by 15 million people.
In a press release by Mindscape Entertainment dated July 19, 1999 , another report from PC Data is cited according to which "Doom" sold 2.9 million copies between 1994 and 1999. It is not clear whether this refers to Doom and Doom II, Doom and Ultimate Doom, or some other combination. If it refers to Doom and Doom II, it is inconsistent with the aforementioned figure from PC Data which puts the combined sales for shareware Doom and Doom II at 3.2 million (the difference of one year hardly provides sufficient explanation; it would imply that in the first 20 days after its release, shareware Doom sold 300,000 more copies than Doom and Doom II did combined in 1999). It does however make some sense if taken to mean Ultimate Doom and Doom II combined. In any case, it can probably be ignored in favor of the more specific numbers from the 1993–1998 report and the Handbook.
- Shareware registrations turned in $100,000 per day immediately after the release (Masters of Doom, page 161).
- Doom II's initial release was 600,000. The supply was intended to last one quarter, but only lasted one month (Masters of Doom, page 182).
- Doom II has sold for over $100 million ($80 million in the United States, $20 million in Europe of which 30% in Germany). The retail version of Ultimate Doom has sold for over $20 million in the United States. (PC Data, 2000, cited in Masters of Doom, page 210)
- Doom II was the second best selling CD-ROM game of 1994 (PC Magazine, June 27, 1995, ).
- id Software got $250,000 from Atari for the Jaguar port of Doom (Masters of Doom, pages 174-175).
- Due to rampant piracy in Asia, id Software sold the rights to sell the game to the biggest pirates for $1 per copy (John Romero's image archives )