I am looking for a precise definition for a blunder. Computers often flag moves as blunders for any move that loses a point advantage or more. But what if I am completely winning and I decide to simplify the game by "sacrificing" my material plus. The computer may say that I lost more than a point advantage, but am I not more likely to win? There is also the scenario where a move may improve your position as evaluated by the computer but greatly decreases your chance of winning. Thus, I am interested in opinions on defining a better definition of a blunder than the computer uses.

  • The best way to learn things is on examples so in addition to those great definitions cited by collegues above I'm just going to paste you this: youtube.com/watch?v=TY41yF1gX1w as a greatest example of what blunder is.
    – Pijotrek
    Commented Oct 5, 2014 at 6:48
  • 2
    After you have decided on a definition, you may also edit the blunder tag wiki. Commented Oct 5, 2014 at 14:42

3 Answers 3


The first English definition of blunder I see is "a stupid or careless mistake", and that's how I have always perceived the term in chess. It's not the severity of the error that matters so much as how silly and avoidable it is. If you played a move that takes the evaluation from 0 to -10 because you missed all the implications of a spectacular sacrifice that needed to be calculated out to 10 moves to verify its soundness, that's not a blunder, but if you played a move that takes the evaluation from 0 to -1 because you just didn't notice that a pawn was hanging, that is a blunder.

  • 2
    +1, this is how I've heard the term used. If the player who made a mistake can't easily see why the move was bad after someone points it out, it's never called a blunder, even if the mistake was very bad.
    – JiK
    Commented Oct 6, 2014 at 8:58
  • It's gotten a couple of downvotes, so I guess our mutual understanding of the term is not universal!
    – dfan
    Commented Oct 6, 2014 at 12:20

This is an interesting question. It seems that the higher the skill level, the less it takes to consider something a blunder. A GM may consider getting double pawns in a certain position a blunder while weaker players may just see it as a mistake or may not even call it a bad move. So how you call a blunder depends on your skill level because higher level players can better take advantage of all ranges of mistakes compared to weaker players.


A blunder is a move that gives your opponent enough of an advantage to win, or to get a draw after you should have won.

As someone else pointed out, it depends on the skill level. At a high level, the "loss" of a move or a key square may be a blunder. For intermediate players, maybe the loss of a pawn, and for beginners, maybe one or more pieces.

That is, these "advantages" are large enough, relative to the skill level, that upon seeing one of them, you can reasonably predict the likely winner.

  • Isn't also a blunder to misplay a winning position and transform it into a draw? Commented Oct 5, 2014 at 14:09
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    @pablo: Added "or to get a draw after you should have won." to first line.
    – Tom Au
    Commented Oct 5, 2014 at 14:16
  • I'd say it's also blunder to transform a easily won position to a (still winning) position where a hard fight is needed for a win (for example, missing a mate in one in an advantageous endgame). It looks like you disagree; is that so?
    – JiK
    Commented Oct 6, 2014 at 12:23
  • @JiK: We're all human, and no one plays perfectly. To me, a blunder is where you play "below your level" and that of your opponent. So losing a pawn wouldn't really be a blunder for a beginner, but would be for me, an intermediate player. Likewise, I wouldn't "fault" myself for losing a move or a square, but would fault a GM.
    – Tom Au
    Commented Oct 6, 2014 at 13:30
  • @TomAu I'm sorry, I don't see how your comment is related to my question.
    – JiK
    Commented Oct 6, 2014 at 13:36

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