I heard that the value for the king as an attacking piece is 4 -- slightly better than a bishop or knight. 

However, it can't capture protected pieces, or step into the line of fire of an enemy piece. I wonder why he deserves a 4.

Any thoughts?

It doesn't really matter, since there are no trades involving a king.

But in the endgame, it's essential for a win... or a draw.

I like the way the Queen is an all powerful woman, while the King has to mainly cower behind pawns, or timidly move one square at a time. 

I'm talking about strength.

You're right. I can't believe we such a cowardly person leading an army.

I think the king's value is infinity.

Why?

Cause if you lose it the game is over.

I did say as an attacking piece. Therefore, in terms of his abilities, ignoring the fact that he is a monarch.

Game Value : The Game

Atk Value    : 3?

The king doesn't have a value because it is traditionally not taken and giving it a value doesn't seem to carry much of a point but if it were to possess some sort of value it would probably be the infinite summation of every piece in the game squared by the number of squares on a chess board (It's much more than 64, look closely!).

Yes, but the numeric values of pieces are mainly intended to give beginners a thumb rule to evaluate their trades, that's why giving the king a value is not very useful.

Maybe so. 

However, I wasn't the first one who tried to assign a number to the king. 

I just wanted peoples' opinions. Thank you for sharing!

As it can't be traded any numerical value is meaningless.

The value of other pieces is purely there as a trade guide, but remain fluid throughout the game. For example, what value do you give a passed pawn at the 7th rank, or 2 Rooks controlling the e file, or a Knight forking your opponents King and Queen?

I know. That's why I gave you mine.

I've always been told that a king can be as powerful as a rook in an endgame so it's essential to involve him.

i Think that giving it a fighting value is good because that is how much you should invest in checkmating him

I feel 4 or 3 are around right, as it's ability to move in any direction gives it an edge comparable to that of the knights and bishops. Although this would mainly be used for defense, considering it's one-square range. There's a reason it takes some effort to get it trapped I guess.

That's not an opinion, that's a repitition of a well-known fact, which is slightly irrevelant.