# How important is castling? How much is it worth?

Are there some statistical values for the worth of castling? Are there some numbers, for example in centipawn that can represent the value of castling?

• Notice that in general there is no objective value of things, it all depends on the position. If you castle into your opponent's rooks on open file, then of course it is not a good move, for instance. Jul 19, 2017 at 13:30
• I am thinking about it, because I want to know when if should concetrate on development if there is a good possibility to destroy opponents castling. Maybe for the cost of 1 pawn or 2-3 moves Jul 19, 2017 at 13:36
• Do you want how much it should worth in chess engine or are you are interested in chess itself? Your response will define your answer. Jul 19, 2017 at 14:00
• I think i interested in both answers. But my question is a little bit more related to the chess engines Jul 19, 2017 at 14:09
• @GennaroTedesco Your statement is wrong. Castling is an engine parameter and is well defined in chess engine programming. It does have objective value. Jul 19, 2017 at 14:46

The reason for this, however, it is not because castling is dependent on the position. The argument that castling cannot have a value because it can lead to getting mated or because it can lose you the game is essentially flawed since for this same logic a queen cannot have a value because saving a queen can also lead to get mated or lose you the game. My reasoning for this lies on the following statistic of utilization of squares by chess Grandmasters. It is quite obvious that using both white and black, Grandmasters tend to castle in almost every game: `g1` as white and `g8` as black have almost always a value greater than `1`, meaning that the king is usually tucked in the corner for safety. Thus I would say that castling is, in average, a borderline indispensable tool that ensures the king safety.

Protecting one's king and checkmating the opponent's is the objective of the game, meaning that there is no need to assign a numerical value to the king because losing it means that the game is lost. Similarly, taking away one's option to castle severely hinders the safety of the king and, as seen above, is used virtually in every game. Hence castling cannot have a numerical value assigned since virtually every strategy to defend one's king uses it.

• This is a very insightful answer. I'd add that protecting the king is the most important aspect of castling but not the only aspect. Because the king ends up tucked away on completion a side benefit of the 1-tempi move is that a powerful but marginalized piece (rook) is brought front and centre where he can go on to dominate centre columns. This secondary benefit goes on to shape all subsequent game play (so no incidental benefit) Jul 24, 2017 at 15:17
• Wow, Judit Polgar really likes 1.e4 openings. Jul 26, 2017 at 8:34
• In all honesty, are you advocating that I never dare to assign the number ever to anything? If so, you are too extreme for me to consider correct. You say: `... is essentially flawed since for this same logic a queen cannot have a value`. That sounds like you're saying that I should stop assigning "9" to a queen in all positions. Again, acknowledging complexity doesn't mean we get extreme. Mar 19, 2018 at 22:57
• `Hence castling cannot have a numerical value assigned `. You're literally wrong. Computers do this in positions. The option of casteling has a number assigned to it. If it's the highest, that move is done. If not, it's not done. In addition to that wrong statement, I fear this answer has too many illogical non-sequiturs in it; For example: just because I plan on casteling at some point, doesn't entail that there's never, ever a reason to assign a number. For example, should I castle now in move 3 and lose a pawn? or wait to castle later and save it? This is a real decision we often face. Mar 19, 2018 at 23:18
• Read my answer again. I use an example to say why some logic is flawed, I never say that you should stop assigning values to pieces. Also, since the OP is asking for statistical values, he wants a fixed one in the same way there is a fixed statistical value for the pieces. What computers do are evaluation functions that change, they do not assign a fixed value to castling, it depends on the position. Your comments are exactly the reason why I added the preface of flawed logic to my answer. Mar 21, 2018 at 17:33

Yes there are some numbers that can (sort of) represent the value of castling.

If you let Stockfish or any other strong engine analyze the starting position, it will generally come to the conclusion that White has roughly a +0.50 advantage. But if you use an opening book (1. Nf3 Nf6 2. Rg1 Ng8 3. Rh1 Nf6 4. Ng1 Ng8 5. Nc3 Nf6 6. Rb1 Ng8 7. Ra1 Nf6 8. Nb1 Ng8) which lets Black castle but not White, the advantage actually flips around, and the starting position advantages Black.

Check these games out:

• Stockfish-Xiphos. The starting position, except White can't castle while Black can. Stockfish's starting eval at depth 31/48 is -0.20. (Yes Stockfish wins anyway, but it is Stockfish, the strongest conventional engine in the world, playing)
• Xiphos-Stockfish. The reverse game. Xiphos plays 1. Nc3 evaluating the position as 0.00, while Stockfish is -0.84 at depth 36/52.
• AllieStein-Stockfish. Played from the opening position with both sides able to castle. AllieStein gave 0.43 advantage to White at depth 18/57.
• Stockfish-Alliestein. The reverse game, Stockfish gave White a 0.47 advantage in the opening position at depth 38/59.

If you think of castling as an efficient way to play, say, Ke1-f2-g1 and Rh1-f1, then castling takes one tempi vs. three tempi to castle by hand. Therefore castling is worth three tempi.

• I don't think you can approximate it like that. Castling by hand puts the king in an even less safe spot temporarily (f2/f7 is a weak point that the opponent can usually attack relatively easily) and also requires the f pawn to be moved (a fourth tempo spent on a move that permanently weakens your position more often than not) Jul 20, 2017 at 6:24
• Hmm. The difference between one tempo and three tempi is two tempi, isn't it? So the right to castle is worth two tempi? But your calculation applies only when the rook's final destination is the f file. If we compare Ke1-f2-g1 & Rh1-e1 vs. O-O & Rf1-e1, castling only saves one tempo.
– bof
Jul 20, 2017 at 23:13

I would check this by trying some experiments with a chess program to see how it evaluates positions. For example you could put in a position where one side is not castled and then the same position, if it is possible given the position, with the same side castled and compare the evaluations. You could do a similar test with the original position where the one side is not castled, but is able to castle, versus the same position but where the one side is not able to castle - because the king or rook already moved. Of course the evaluations would depend on the initial positions. If the positions are closed and not much is going on, you'd probably get a more stable value for castling from the experiments.

• Yes! Computers literally assign centipawn values to casteling. Therefore this intrinsically answers the OP's question "Are there some numbers, for example in centipawn that can represent the value of castling". This answer also acknowledges that there's no single number to rule all positions. Mar 19, 2018 at 22:53

Chess has one particular tactic or theme which cannot be ignored and that is king safety.

Since the rule is that if the king is lost, or checkmated, the game is lost; so the value of king is the most essential. I do not say that castling is the only answer to a safe king since there are many noteworthy games which have been won without castling, but castling is a standard procedure in many openings, and middlegames, since the king goes inside the high walls protected by its own soldiers, and gets the rooks connected.

The value of Castling increases because beside the King the Queen and the minor pieces are developed somewhere else in the Game . What I mean is playing with White the King's Bishop is developed on b5,c4,e2 or g2 mostly . The Knight is developed frequently on f3,e2 or a3 sometimes and we put our e and d pawns on e4 and d4 in most cases . The Queen leaves the stand from d1 and gets developed to some other Square .Now when it happens if the King remains in Centre it becomes exposed and susceptible to attack . No minor pieces are there to protect it .

When the King remains in the Castle then the Knight on f3 , the Pawns on f2,g2 and h2 serve as a barrier and the Rook stays besides as if the King is riding on a high elephant . Sometimes with the g pawn on g3 the Bishop stays on g2 . The King is protected and then the Forces can be coordinated on a particular area of the board for an attack . So Castling makes just too much sense .

• I don't think this answers the question. The question is very specifically about assigning a number to the worth of casteling. It's possible you think that the OP's motivation is a bad one, but that would mean you upvote the other answer saying so. Mar 19, 2018 at 22:44

I am conducting some runs right now with some fairy armies battling each other and FIDE. I am thinking of taking away castling as an option from the slightly overpowered armies to better balance the games. Slightly overpowered armies are fairy armies with win% greater than 50% but less than 60%. The error rate of the samples is high, even at 200+ games, so it is difficult to calculate the true mean with precision, but I bet this will make the difference. I am betting half a pawn.

• Wow. Just did it yesterday and it made a big difference, at least a pawn’s worth of value. To be clear, I removed castling as an option from one of the armies, and the formerly dominant army consistently began to lose from that one small change. When I have time, I will check it on a standard game and get back... May 7, 2020 at 14:33

The rule is you have to castle in the first 10 moves, otherwise you will leave your king unprotected.

Most amateur players launch an aggressive attack and leave the king sitting there without any protection. If you study games from professional players, you will notice that they castle early in the opening.

• ... except when they don't. Professional players know when castling is less important than other urgent matters. Jul 19, 2017 at 17:24
• "Centralization and development are worthless as opening principles unless they are complemented by and abiding solicitude for KING SAFETY." from The Secrets of the Russian Chess Masters: Fundamentals of the Game book. Jul 19, 2017 at 17:39
• To back up the point of @Glorfindel, you can take as an example many lines in the Najdorf Sicilian (specifically the English attack) where Black plays ...h5 and doesn't castle at all - or the famous Poisoned Pawn variation, all worked out to be at least equal for Black. Jul 19, 2017 at 20:40
• No. I'm not a professional player, but I like castling. Why first 10 moves?? Professional players don't castle early. I give this answer -1. Jul 20, 2017 at 2:04
• @SmallChess ..except when they do. In some openings, professional players castle as early as in the fourth move (spending the first three for the minimum requirement of moving a pawn and the minor pieces out of the way) - for example, the modern Giuoco or the Nimzo Indian. The rule is that there is no rule (and certainly none with a fixed number of moves). Castling early is beneficial on average, but, as Glorfindel wrote, there are situations where other things are more important. Jul 20, 2017 at 6:15