What is a blunder in chess?
A blunder loses 200 centipawns or more against the engine's best line — two pawns' worth of advantage. It is the grade at which the likely result of the game changes.
Threshold
Blunder — 200 centipawns or more lost against the engine’s best line.
Where the threshold sits
A centipawn is a hundredth of a pawn, so 100 centipawns is a whole pawn's worth of advantage. At 200 the loss is two pawns, which in most positions is decisive between players of similar strength.
Hanging a piece is the obvious case, but so is missing a forced tactic, allowing a fork that wins the exchange, or trading into a lost endgame. The engine does not care which it was — it measures only what the position was worth before and after.
The pattern matters more than the move
Any single blunder is mostly noise. Everyone hangs pieces in time trouble, and reviewing one game tells you that you hung a piece, which you already knew.
What is worth knowing is whether they cluster — in one opening, as one colour, in one time control, or past a certain move number. That is a question about a history rather than a game, and it is the one this app is built to answer.
Frequently asked questions
How many centipawns is a blunder?
200 or more. Below that, 100 to 199 is a mistake and 50 to 99 is an inaccuracy.
Why do I blunder in winning positions?
It is the most common place to blunder. A winning position invites relaxation and often has more pieces in contact, so there are more ways to go wrong — and the eval drop is larger because there was more to lose.
How do I stop blundering?
Generic advice — check every check, capture and threat — helps less than knowing when you personally do it. If your blunders cluster after move 30 in blitz, the fix is a time-management one, not a tactics one.