We analyzed the latest 1,487 games of 160 Chess.com players rated under 800 with the Stockfish engine. Here is what goes wrong most often for them, how often, and what it usually costs.
Data from 160 players' games, updated 2026-11-14. A player's rating is the middle of their ratings across those games.
You had a fork available that would have won material, but played a different move instead.
Players rated 800 to 1199 do this 1.7 times per 100 moves, less often.
You left a piece completely undefended, and the opponent could capture it for free.
Players rated 800 to 1199 do this 1.1 times per 100 moves, less often.
Your pieces were left on squares where the opponent could fork two at once, winning material.
Players rated 800 to 1199 do this 1.0 times per 100 moves, less often.
You fell behind early: an opening move caused a big drop before move 8.
Players rated 800 to 1199 do this 0.6 times per 100 moves, less often.
Your move allowed a forced checkmate that a different move would have stopped.
Players rated 800 to 1199 do this 0.6 times per 100 moves, less often.
You could have won material here but missed it.
Players rated 800 to 1199 do this 0.6 times per 100 moves, less often.
Every player here has run a Blackbox Chess report. Each month we take their newest games from the last 60 days on Chess.com, up to 10, and run them through Stockfish with the same rules our reports use today, so every band is measured the same way. "Per 100 of their moves" counts only the player's own moves. A rating band needs at least 100 players before we publish it. How we check games.
Averages describe a group, not you. See which of these show up in your own games: your first 10 games are free, with no account.
Run my free report