Earlier today we reported that a former Half-Life 2 mod turned commerical product called Garry's Mod had generated over $3 million in sales just by being on Valve's Steam service. Today Gamasutra has an article that reveals how many games Valve itself has sold. There's a big catch, however. The numbers are only for retail sales of Valve's products. They don't include the number of units sold from the Steam service.

Valve has always kept specifc numbers related to its Steam service to itself but there have been hints that those numbers are considerable. Even Valve's own CEO Gabe Newell has said he expects Steam sales of its games to surpass retail sales numbers.

So while these figures don't really give the whole picture here are Valve's own numbers on the retail sales of its games so far. The numbers do not include Valve's just released zombie co-op shooter Left 4 Dead. They also, for some unknown reason, don't include sales of the stand alone version of Day of Defeat which Activision released in 2005. Finally they don't include the retail sales of the PC versions of Team Fortress 2, Portal and Half-Life 2: Episode 2 which were released as separate products several months after the release of The Orange Box.

Half-Life: 9.3 million units
Half-Life Opposing Force: 1.1 million units
Half-Life Blue Shift: 800,000 units
Counter-Strike: 4.2 million units
Counter-Strike Condition Zero: 2.9 million units
Counter-Strike Source: 2.1 million units
Half-Life 2: 6.5 million units
Half-Life 2 Episode 1: 1.4 million units
The Orange Box: 3 million units