Chess Move Classifications Explained: Brilliant to Blunder

You finish a game, run the review, and every move comes back wearing a label. A green Best here, a yellow Inaccuracy there, the occasional red Blunder you already regret. The colors are easy to read. What each grade actually measures, and why a move that felt fine scores as a Mistake, takes a bit more explaining.

The grades are not opinions. Each one comes from a single measurement applied to every move the same way. Once you know what that measurement is, the labels stop reading as a verdict and start telling you where a game slipped and by how much.

Every Grade Comes From One Number

Stockfish evaluates a position and produces a score, traditionally in centipawns, where +100 means you hold roughly a pawn's advantage. Centipawns judge a move badly, though, because the same swing means different things in different positions. Going from +200 to +100 changes nothing; you are still winning in comfort. Going from +50 to -50 flips the game. Raw centipawns call both a 100-point drop. They are not the same drop.

So the grades run on win probability instead. Every evaluation becomes a percentage: how often a player wins this position from here. A move is then judged by how much of your winning chances it gave up against the best move available. If the best move keeps you at 70% and you play something that drops you to 55%, you lost 15 points of win probability. That figure, the win-probability loss, sets the grade.

This is why a small centipawn change in a knife-edge position can be a Blunder while a larger one in a lopsided position barely registers as a Good. The engine tracks how much the move changed the result, not the size of the number.

The Everyday Grades: Best Through Blunder

Six grades cover the moves you make in every game. They sit on one scale, ordered by how much win probability the move surrendered:

• Best — you found the engine's top choice, or gave up under 1% win probability. Nothing better was on the board.
• Excellent — not the very top move, but within about 3.5%. You kept everything that mattered.
• Good — a sound move that cost up to 7% or so. Short of ideal, and no one is punishing you for it.
• Inaccuracy — a drop of about 7 to 10%. A stronger move existed, but you have not handed anything decisive to your opponent.
• Mistake — a 10 to 20% loss. A real error that gives your opponent a tangible advantage a good player will notice.
• Blunder — 20% or more. The move that changed the game. Most rated points below master level are won and lost on blunders, which is why they are the first thing to study.

The gaps are set on purpose. No game is a string of perfect moves, so the top three grades leave room for the many that are simply fine. The bottom three spread wider, because that is where the damage lives and where your review is trying to point you.

The Special Grades

Four more labels sit off the Best-to-Blunder scale. They describe what kind of move you played rather than how good it was.

Brilliant

The rarest grade, and the one people screenshot. A Brilliant move is a strong move that also sacrifices material: you give up a piece or an exchange, the engine still likes your position, and the sacrifice is real rather than a piece that was doomed anyway. All three conditions hold at once. A queen sac that mates on the spot in a position you were already crushing will not qualify, because the point of a Brilliant is finding a genuine sacrifice while the game is still live and having it work.

The bar is that specific, so you can play a hundred strong games without one. A Brilliant is a special event, not a report-card grade.

Great Move

A Great Move is the only move that holds. The engine asks a second question of your best move: how bad is the second-best? When every alternative would throw away a large chunk of your winning chances and you found the one move that keeps them, Best gets promoted to Great. This is the label for threading the needle, whether that means the single defense that saves a lost-looking position or the one accurate continuation in a sharp line.

Book

Early moves that follow established opening theory get marked Book instead of scoring on the win-probability scale. This covers the first several moves, while the position is still known territory. Book says nothing about the quality of your play; it means there is nothing to analyze yet. The grades start doing real work once you leave the opening and begin making your own decisions.

Miss

A Miss is the flip side of a Blunder, and most players skim past it. It fires when you had a genuine chance, a tactic or a winning shot, and played something else that let it go. You may not have lost material or hung anything. You failed to gain. A missed win is a full result left on the table, which is why these sting more than the label suggests. A review full of Misses points at a different problem from a review full of Blunders: you are not seeing the good moves when they are there.

Forced

With exactly one legal move, there is nothing to grade, so the review marks the move Forced. It carries no judgment, since you chose nothing.

How to Actually Use the Grades

Treat the grades as a map rather than a scoreboard. The score at the top says how the game went; the labels say where to look. A focused review runs about the same length either way, so spend it on the moves that decided things:

1. Go straight to the Blunders and Mistakes. These hold your rated points. Cover the board at each one and decide what you would play now, before you read the engine's answer. The gap between your instinct and the right move is the lesson.
2. Read the Misses as seriously as the Blunders. A missed win costs as much as a bad move and feels like less. More Misses than Blunders means your training should lean toward tactics and calculation rather than "stop blundering."
3. Skip the Excellents and Goods. They confirm you played fine. Chasing a board full of green is how people burn review time.
4. Watch for repeats across games. One hanging piece is a slip. The same pattern flagged in four games this week is the most valuable thing you can fix. Our guide to analyzing your games like a grandmaster builds that into a weekly routine.

You can run this on every game you play, with no daily limit, which is what makes the pattern-spotting possible.

Why Your Grades Won't Perfectly Match Chess.com's

Review the same game on two sites and most moves land on the same grade, though a few differ by a step and the label names vary. Both rest on the same idea, win probability lost as measured by Stockfish, so a real Blunder reads as a Blunder anywhere. The differences come from three places: the exact thresholds each site draws between grades, the depth the engine reached, and the criteria for special labels like Brilliant, which every site writes its own way. A move sitting on the boundary between Good and Inaccuracy falls to whichever side the ruler favors. That is normal, and it does not make either site wrong.

Frequently Asked Questions

What's the difference between a Mistake and a Blunder?

Size. A Mistake gives up roughly 10 to 20% of your winning chances; a Blunder gives up 20% or more. Both are worth reviewing, and blunders are the ones that usually decide the result.

Why did I get a Mistake for a move that didn't lose material?

Because grades measure win probability, not material. Allowing a strong pawn break, walking into a bind, or missing your opponent's threat can cost more of the game than a lost pawn, with nothing captured.

Is a Brilliant move always the best move?

Yes. A Brilliant is a Best move that also happens to be a sound sacrifice, so it can never be a bad move. A sacrifice that does not work is a Blunder, not a Brilliant.

How is a Miss different from a Mistake?

A Mistake worsens your position. A Miss leaves a much better opportunity on the table, so you keep what you had instead of losing ground.

Do the grades depend on the analysis depth?

Some. Deeper analysis produces steadier evaluations, which can shift a borderline move between two neighboring grades. The default depth grades a full game in under a minute and is accurate enough for study; raising it sharpens the call on the few moves sitting on a threshold.

See Your Own Moves Graded

The quickest way to learn the labels is to watch them land on your own play. Import a recent game, let the engine grade every move, and start with the reddest one on the board. That move has the most to teach you.