# What counts as a blunder in chess?

> A blunder is a move that throws the game away, turning a winning or level position into a losing one, most often by missing a threat.

By Chesslord · Published November 3, 2026

A blunder is the worst kind of bad move. It is not a move that is merely weaker than the best one: it changes the result the position was heading for, from a win to a draw, or from a draw to a loss. In annotated games it is marked with ??.

## What makes a move a blunder rather than a mistake?

The difference is how much the move gives away. An inaccuracy gives away a little, a mistake gives away a lot, and a blunder gives away the game, or most of it. What decides it is not how the move looks, but what the position was worth before it and after it.

| Label | What it usually means |
| --- | --- |
| Inaccuracy | A small part of the advantage is given away |
| Mistake | A large part of the advantage is given away |
| Miss | A winning chance is left on the board |
| Blunder | The result itself is given away |

## How do reviews measure it?

An engine evaluates the position before and after each move. Measured in pawns, the same loss means very different things in different positions: a pawn lost while a rook up changes little, while a pawn lost in a level endgame can decide the game.

That is why some reviews, including the Chesslord [game review](https://chesslord.app/chess-com-game-review), measure what each move cost in the chance of winning rather than in pawns.

## Why do players blunder?

Most blunders do not come from knowing too little chess. They come from not looking. The usual causes:

- A piece left where it can be taken for free
- A check, capture or threat of the opponent that was never looked at
- Time trouble, when there is no time left to check
- Relaxing in a position that already looks won

## How do you blunder less?

Before every move, ask what your opponent's last move threatens, and look at every check, capture and threat your own move allows. Then go back over your games: a review shows the moves that cost the most, and the same pattern tends to come back.

## Questions

### Is every losing move a blunder?

No. In a position that is already lost there is nothing left to throw away, so a bad move there is rarely called a blunder.

### Do strong players blunder?

Yes. Grandmasters blunder too, most often when they are short of time.

### What do ?? and ? mean in a game score?

In annotated games ?? marks a blunder, ? a mistake and ?! a dubious move.

## Sources

- [Blunder (chess), Wikipedia](https://en.wikipedia.org/wiki/Blunder_%28chess%29)
- [Chess annotation symbols, Wikipedia](https://en.wikipedia.org/wiki/Chess_annotation_symbols)

Where Chesslord comes in

[A game reviewed move by move](https://chesslord.app/chess-com-game-review)

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