Castling is a very special ability that helps safeguard your King and activate your Rook. It is the only time you can legally move two pieces in one turn! Chess gurus tout the benefits of castling, but how do you castle in chess? 

This article will mainly focus on the rules of castling – check out the 3rd point of “Chess Opening Strategy” for more pros and cons about castling (ARTICLE COMING SOON!).

What is Castling

When you castle, you move your King two squares towards one of your Rooks, and then that Rook “jumps over” your King to the opposite side. It’s easier to visualize with an example.

You can castle on both the Kingside and the Queenside. Castling on the Kingside is called “short castling” because the Rook moves only 2 squares, whereas castling Queenside is “long castling” because the Rook moves 3 squares.

The Kingside is the side of the board closer to the King (i..e. columns e-h), while the Queenside is the side of the board closer to the Queen (i.e. a-d).

In notation, Kingside castling is denoted as “0-0” and Queenside castling is “0-0-0”.

Note: Whether you castle Kingside or Queenside, the King always moves 2 squares and the Rook moves to the far side of the King.

Rules of Castling

There are 4 rules to castle. Watch carefully if your opponent breaks these rules while castling – perhaps the most common illegal move is castling illegally. [Read the official USCF Castling Rule in our helpful article]

Even history’s most famous chess grandmasters sometimes forgot how to castle!

Rule 1. Cannot castle if your King or Rook has moved.

This rule is self explanatory. You cannot castle if your King or Rook (the one you will move to castle with) has moved before, then you can’t castle.

Note that this doesn’t apply to the other Rook – that one can move.

For example, if you want to castle Kingside and you haven’t moved your King or h1-Rook, then you meet Rule #1 even if you moved your a1-Rook.

Rule 2. Cannot castle through Other Pieces

This rule is also self explanatory. You can’t castle if there are pieces in the way – no, your king and rook don’t magically take them ;( . It would be like trying to drive a car through a wall – it ain’t gonna happen.

Rule 3. Cannot castle if your King is in check

Many times beginners try and teleport out of a check by castling. Unfortunately, that’s not allowed. Make sure your opponent doesn’t do this!

This is one of the most forgotten rules. Make sure your opponent doesn’t castle if they are in check!

Rule 4. Cannot castle “through” check

This is probable the most confusing rule on the list. Basically, you are not allowed to castle if any square that your King would pass through is attacked by an enemy piece. The logic is that your King would technically be in check if it moved through those squares to castle, and it’s illegal to put your King in check.

Common Confusion Points:

1. You can castle if the rook is attacked. This is what the world champion challenger Viktor Korchnoi forgot.
2. On Rule 4: You can castle even if your Rook passes through a square that is attacked. For example this is legal.