There is no question about it; Fallout 4 will be the most commercially successful game of 2015. Bethesda’s open-world title was released yesterday and in just 24 hours, Fallout 4 has sold more than 1.2 million copies on Steam.

This information comes from the creator of SteamSpy. As he noted, it will take around 3 days for SteamSpy to catch up with the real sales of Fallout 4.

Fallout 4 had around 1.2M owners on Steam on day 1.

It will take 3 full days for my site graphs to catch up, sorry.

— Steam Spy (@Steam_Spy) November 11, 2015

In addition, SteamSpy has revealed the conversion rates for previous Fallout games owners into 1-day Fallout 4 purchasers on Steam.

Conversion rates for previous Fallout games owners into 1-day Fallout 4 purchasers on Steam. Skyrim for comparison pic.twitter.com/Go3nbU2HpM

— Steam Spy (@Steam_Spy) November 11, 2015