The Most Common Chess Opening Mistakes, by the Numbers

Of 6,572 catalogued mistakes, only 476 (7.2%) are full blunders. The overwhelming majority — 3,954, or 60.2% — are inaccuracies: technically suboptimal but rarely losing outright. This matches what coaches see in practice: club-level games are usually decided by an accumulation of small imprecisions rather than one dramatic error.

The Richter-Veresov Attack: h6 tops the severity ranking at 755.7 centipawns average loss per mistake, followed by the Alekhine Defense: Normal Variation: Nc3 (715.0) and the Trompowsky Attack: h6 (674.7). These are positions where the 'obvious' or tempting move is a sharp trap — the gap between the natural-looking move and the computer's best move is unusually wide.

The most expensive individual blunder in the corpus is Qf3 in the Danish Gambit Accepted: Bc4 line, costing 958 centipawns against the correct Bxb2 — nearly a full piece's worth of advantage handed over in one move. A near-identical trap appears in the Sicilian Defense: Smith-Morra Gambit Accepted: Bc4, where the same Qf3-instead-of-Bxb2 pattern costs 942 centipawns, suggesting this is a recurring tactical motif across multiple gambit-accepted structures rather than a one-off.