This is how it has broken down so far (more or less): Season 1 (2011): A Game of Thrones Season 2 (2012): A Clash of Kings Season 3 (2013): The first half of A Storm of Swords (aka Steel and Snow )
Season 4 (2014)
: The second half of A Storm of Swords (aka Blood and Gold ) Season 5 (2015): Both A Feast for Crows and A Dance with Dragons and new material Season 6 (2016): Both A Feast for Crows and A Dance with Dragons and new material
We also know: Season 7 (2017):
Unpublished material and new material Season 8 (2018): Unpublished material and new material Seasons 1 and 2 were a book each, but it was changed for Season 3, which became the first half of Storm of Swords , and Season 4 became the second half.
The producers then, somewhat surprisingly, managed to squeeze the next two books, A Feast for Crows and A Dance with Dragons , into Season 5, by removing lots of what many people saw as extraneous plot lines.
It's worth noting that there has has been some overlap.
Certain events have drifted into different seasons, so the above isn't always strictly true -- just mostly true.
Season 6 took most of its story from The Winds of Winter (although there were some unused things from A Feast for Crows and A Dance with Dragons that appeared in it).
George RR Martin confirmed this in a Vanity Fair article (" George R.R. Martin Has a Detailed Plan For Keeping the Game of Thrones TV Show From Catching Up To Him ").
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That's the plan.
Seasons 1 and 2 (so far) are a book each.
Though this might change for book 3 (Storm of Swords), which is a lot bigger than the first two.
In this interview , George R. R. Martin admits that its going to be hard to fit book 3 into a standard season.
Relevant quote follows:
The real crucial point comes with the third season with Storm of Swords.
Storm of Swords is a monster of a book, a gigantic book.
It's 500 pages longer in manuscript than Clash of Kings was.
And Clash of Kings was 100 pages longer than Game of Thrones.
You cannot do Storm of Swords in 10 hours.
I think they need to make two seasons out of that.
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For a more exhaustive chapter-to-episode breakdown derived from Joel Geddert's Game of Thrones episode chapter coverage interactive table (Note: contains chapter titles with POV character names): Season 1 A Game of Thrones: 69 of 73 chapters A Clash of Kings: 1 of 70 chapters Season 2 A Clash of Kings: 55 of 70 chapters A Storm of Swords: 5 of 82 chapters Season 3
A Clash of Kings: 1 of 70 chapters A Storm of Swords: 44 of 82 chapters A Dance with Dragons: 1 of 73 chapters Season 4 A Storm of Swords: 20 of 82 chapters A Feast for Crows: 1 of 46 chapters A Dance with Dragons: 2 of 73 chapters Season 5 A Storm of Swords: 3 of 82 chapters A Feast for Crows: 17 of 46 chapters A Dance with Dragons: 25 of 73 chapters
The Winds of Winter: 2 of ??
chapters Season 6 A Storm of Swords:
1 of 82 chapters A Feast for Crows: 6 of 46 chapters A Dance with Dragons: 2 of 73 chapters The Winds of Winter: 1 of ??
chapters
Note that some book chapters have not been covered on the TV show either because events were changed or cut from the TV show, and that the more the show has continued, the more it has invented new material of its own.
For another good reference, the Boars, Gore, and Swords podcast is experiencing the TV show before the books and they have been doing a book club after each season.
Check out their episode guide .
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Now that season 4 has ended as well, it would be good to point out that the third book, A Storm of Swords has been broken in two seasons: season 3 and 4.
But also, in those two seasons (especially the fourth one), there were a lot of chapters from the fourth and fifth book; like for instance the chapters with Reek and some of Brienne's.
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I remember reading somewhere that this is indeed the plan: each season is roughly equivalent to one book.
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It used to but it doesn't anymore.
The first 3 seasons and the first two book + part 1 of the third line up almost perfectly.
Season 4 is still kinda the second half of the third book.
After that
no.
It's a mix and match of the 4th book, 5th book, their own material perhaps based on Martins hints and maybe of the 6th book which we wont know until 2020 or later since that's when it'll be out.
Maybe (yeah official date is sooner but every time we get close to it
it's moved up by
a year so).
Season 7 and 8 will be a small part of the 4th and 5th books (for example the whole fake Targeryan), whatever Martin told them, whatever they made up and whatever spoilers for the last two books they have.
How much Book 7 will match anything is a stupid question for now.
Try asking in 2035.
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Does each current  Game of Thrones  season roughly equal one  A Song of Ice and Fire  book? And do we know which future seasons will cover which books?  I am planning to read the first book after the TV show has finished depicting the events in the first book. I would like to know if after each TV season ends I can expect to be able to read a book covering the events depicted on screen?
Does each season of Game of Thrones roughly equal a book?
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Seasons 1 and 2 are equivalent to one book each. The third book has been split between seasons 3 and 4. The Game of Thrones series matched books to seasons for the first 3 seasons. After Book 3 was too large to be fitted into one season and had to be split into 2, the matching became less clear. 
The plan with Game of Thrones was to match a season of the series to a book. This was the case for seasons 1 to 3. Book 3 was so big it had to be split into 2 seasons, and from then on, the seasons do not match the books so clearly.