how many turns does it take to win a magic the gathering game

[Blobby]

how many turns does it take to win a magic game?

[Kenji]

Uh...How many turns? That depends -- how quickly can you drop your opponent from 20 life to 0, or cause them to attempt to draw from an empty library, and so on?

What kind of answer were you expecting? There's no universal answer here. Different decks are designed to win in different ways, and as such will win in a different amount of turns. Also, format is important -- Standard/Modern games often easily last past turn 6-7 or so, whereas Legacy games have a shelf life of 4-5 turns, and Vintage is often over by the first through third turns.