How to use the chess move calculator
- Set up the position. Play the moves on the board, tap ✎ Edit to place pieces anywhere, or paste a FEN or a whole PGN game into the box. Tap White to move to switch the side to move.
- Tap Find the best move. The first time, your browser downloads Stockfish 19 (about 1.9 MB) and keeps it. The engine then thinks for about four seconds on your device.
- Read the answer. The arrow shows the best move. The sentence says what to play and who is better. The table lists the top three moves with the line Stockfish expects. Think longer searches for 15 seconds for a deeper answer.
What the score means
Stockfish scores a position in pawns from White's side: +1.0 means White is about a pawn better, −1.0 means Black is. We show the score to one decimal and turn it into words with this scale:
| Score (either side) | What we say |
|---|---|
| 0.0 to 0.2 | About equal |
| 0.3 to 0.6 | Slightly better |
| 0.7 to 0.9 | Better by most of a pawn |
| 1.0 to 1.4 | Better by about a pawn |
| 1.5 to 2.9 | Clearly better (we say by about how many pawns) |
| 3.0 to 5.9 | Much better, close to winning |
| 6.0 or more | Winning |
| Mate in N | That side can force checkmate in N moves, whatever the other side plays |
The eval bar above the board shows the same score as a share of the bar: the white part grows as White's chances grow, using the win-chance curve chess sites commonly use, so a one-pawn edge moves the bar less than you might expect.
The sample: the Fried Liver position
The board opens on a well-known position from the Two Knights Defence: 1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 d5 5.exd5 Nxd5. White's knight on g5 and bishop on c4 both aim at f7, the square only Black's king defends.
We ran Stockfish 19 lite on it to depth 20 (9 November 2026, the same engine file this page uses). Its top choice is 6.Nxf7, the Fried Liver Attack: White gives up the knight to drag Black's king into the open, scored +0.91. Close behind is 6.d4, the Lolli Attack, at +0.89, so the engine sees two almost equal ways to keep the edge. The quiet 6.d3 scores −0.14: about equal. When two moves score this close, both are good choices; a different depth or device can swap their order.
Why the best move can change
Stockfish searches deeper the longer it thinks. A move that looks best at depth 12 can lose its place at depth 20 when the engine sees further. The depth is shown under every answer. For a game you care about, tap Think longer. Scores within about 0.2 of each other are, for practical play, equally good.
The engine
This page runs Stockfish 19 (lite, single-threaded), compiled to WebAssembly by the Stockfish.js project. The lite build uses a smaller neural network than desktop Stockfish, so it is weaker than the full engine, but it is still far stronger than any human player. It runs inside your browser in a separate worker, so the page stays responsive while it thinks, and nothing about your position is sent to us.
Fair play
ChessMoveScout is for study: puzzles, positions from books and videos, and games that are over. Asking an engine for moves during a game you are playing, online or over the board, breaks the fair-play rules of every chess site and federation. We don't make browser extensions or live-game overlays.
Questions
Is the chess move calculator free?
Yes. There is no sign-up and no limit on positions.
Can it find the best move for Black?
Yes. Tap White to move to switch it to Black to move, or paste a FEN with b as the side to move. Scores are always given from White's side, and the sentence says which side is better.
How do I copy a position from Chess.com or Lichess?
Both sites can show a game's FEN or PGN from their share or export options. Paste either one into the box under the answer and tap Load. A PGN loads the final position of the game; to go through the whole game, use the analysis board.
What does "mate in 3" mean?
The side named can force checkmate in three of its own moves, whatever the other side does.