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Free Chess Calculator — Find the Best Move

Drag pieces to set up any position, paste a FEN string, and find the best move instantly with Stockfish 18.

This free chess calculator lets you find the best move in any chess position in seconds. Set up pieces with drag-and-drop, paste a FEN string, or load a setup from a URL to instantly evaluate any chess position — no account or installation required.

Powered by Stockfish 18 — one of the world's strongest chess engines — this chess position analyzer searches millions of possibilities per second. It returns the top play, three ranked alternatives with evaluation scores, forced mate sequences, and automatic tablebase lookups for endgame positions with seven pieces or fewer.

Whether you need a quick chess position evaluation, want to verify your last move was sound, or are building out an opening or endgame line move by move, this tool covers every use case. Advanced players can chain move responses to explore full variations step by step — all free, with no daily limit.

Stockfish 18 Syzygy 7-piece tablebase Runs in your browser — moves never sent to a server Completely free — no sign-up, no limits Last updated: June 2026

Engine ready on demand

FEN Position

Side to move:

Castling rights: K Q k q

En passant:

Analysis Depth

Example: Analyzing a Chess Position

Here is a real example of the calculator in action. The position below is from the "Immortal Game" — White to move, with a forced checkmate available:

Position (FEN): r1bk3r/p2pBpNp/n4n2/1p1NP2P/6P1/3P4/P1P1K3/q5b1 w - - 1 23
Top Move (Depth 18): Nc7# — Checkmate in 1. Engine evaluation: #1

The calculator identified the forced checkmate instantly. The eval bar shows a decisive advantage for White across all analysis depths. This is the kind of result you get for any position you set up — tactical mates, top alternatives, and a ranked move list.

How to Use the Chess Calculator

Set up your chess position

Drag pieces from the spare piece palette onto the board to build any position, or paste a FEN string directly into the FEN input field. Click "Start Position" to load the standard starting setup.

Set the side to move and castling rights

Click the White (W) or Black (B) toggle to set which side moves next. Check or uncheck the castling rights flags (K, Q, k, q) that still apply. Set the en passant square if relevant.

Choose your analysis depth

Select Fast (depth 12) for instant results, Normal (depth 18) for strong reliable calculation in a few seconds, or Deep (depth 24) for thorough evaluation of critical or complex positions.

Click "Find Best Move"

Press the "Find Best Move" button. The engine searches the position immediately and highlights the optimal response with a green arrow on the board as soon as the result is ready.

Read the evaluation and alternatives

The evaluation score shows who is ahead and by how much (measured in pawns). A "#" prefix means forced checkmate. The top three alternatives are listed with their own scores so you can compare options.

Chain moves to explore a line

Click "▶ Play this move" to apply the suggested move to the board, then calculate again. Repeat to build a complete variation. The move history panel tracks the full sequence in algebraic notation.

How the Chess Calculator Works

Our chess position calculator combines the Stockfish 18 engine, Lichess cloud evaluation, and Syzygy tablebases to give you the most accurate result for any position. Here is a look at the technology behind the scenes:

Depth-First Tree Search

Selecting Fast (12), Normal (18), or Deep (24) controls the number of half-moves (plies) the algorithm searches ahead. At depth 18, it evaluates tens of millions of positions per second — far more of the chess game tree than a human can visualize.

Multi-Factor Position Evaluation

Every position is scored using material count, king safety, pawn structure, and piece mobility. This produces the chess evaluation score via powerful NNUE (neural network) technology — telling you objectively who is winning and by how much.

Principal Variation (Best Line)

Alongside the top single move, the engine returns the full Principal Variation — the sequence of optimal moves for both sides from the current position. This lets you understand the strategic plan behind the move, not just the move itself.

Syzygy Endgame Tablebases

For positions with seven pieces or fewer, the tool queries the Syzygy tablebase — a complete database of perfect play results. The tablebase returns a definitive win, draw, or loss verdict with distance-to-mate — making it the most accurate possible chess endgame calculator.

Frequently Asked Questions

What is a chess calculator?

A chess calculator is an online tool that evaluates any board position and determines the strongest next move. You set up the position on a virtual board or paste a FEN string, and the tool uses a powerful engine to search through millions of possible continuations to identify the strongest sequence. Our free calculator runs Stockfish 18 directly in your browser using WebAssembly — no download or installation needed. It returns the top move, three ranked alternatives with scores, forced mate sequences, and tablebase verdicts for endgame positions.

How do I find the best next chess move?

Set up your position by dragging pieces onto the board or pasting a FEN string. Select which side is to move and confirm the castling rights. Choose your analysis depth — Fast (depth 12) for instant results, Normal (depth 18) for reliable strong moves, or Deep (depth 24) for critical positions. Click "Find Best Move". Within seconds, the engine displays the optimal move as a green arrow on the board, shows the evaluation score, and lists the top three alternatives ranked by quality.

What chess engine powers this calculator?

This calculator is powered by Stockfish 18, the latest version of the open-source engine consistently ranked among the strongest in the world with an estimated Elo rating above 3500. The algorithm runs as a WebAssembly module directly inside your browser — no moves or positions are sent to any external server. For faster initial results, the interface also queries the Lichess Cloud Evaluation API for cached common positions. Deep local computation then overrides these results at your chosen depth.

Is this chess calculator free to use?

Yes, completely free — no account required, no subscription, no usage limits, and no ads. The engine runs entirely inside your browser using WebAssembly, so the analysis costs no server resources and can be offered at no charge. The Lichess Cloud Eval API and Syzygy tablebase lookups are also free external services. The only requirement is a modern browser with JavaScript enabled.

What is a FEN string in chess?

FEN stands for Forsyth-Edwards Notation. It is a standard one-line text format that completely encodes any chess position — piece placements, side to move, castling rights, en passant square, and move counters. The starting position in FEN is: rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1. You can copy a FEN from Chess.com, Lichess, or any chess database and paste it directly into the FEN input field to load that exact position instantly.

What does the evaluation score mean (e.g. +1.23)?

The evaluation score shows how much one side is winning by, measured in pawns. A positive score (e.g. +1.23) means White is ahead by approximately 1.23 pawns worth of advantage, combining material and positional factors. A negative score (e.g. -0.45) means Black is ahead. A score near 0.00 means the position is roughly equal. When the evaluation shows a "#" symbol (e.g. #3), it means there is a forced checkmate in exactly that many moves for the side to move.

What is the difference between Fast, Normal, and Deep analysis?

The depth setting controls how many half-moves (plies) ahead the algorithm searches. Fast (depth 12) completes in under a second and is suitable for quick position checks. Normal (depth 18) is the recommended setting for most positions — it provides strong, reliable moves in two to five seconds. Deep (depth 24) performs an extensive search best used for critical positions, endgame studies, or when you want to verify no hidden resource has been missed. Higher depth gives the algorithm more time to explore the game tree.

What is tablebase analysis?

For positions with seven pieces or fewer (including kings), the calculator automatically queries the Syzygy endgame tablebase. This is a pre-computed database covering every legal position at that piece count — billions of positions total — with the mathematically perfect result stored for each one. The tablebase returns a definitive verdict: win, draw, or loss with perfect play, plus the distance to checkmate. In these simplified endgame positions, the result is not an estimate — it is the provably correct answer.

How accurate is the chess position analysis?

At depth 18 and above, the calculator is extremely accurate for tactical sequences, forced mates, and material combinations. The engine operates at a playing strength estimated above 3500 Elo — far beyond any human player. For complex positional positions, Deep (depth 24+) is recommended. Tablebase results for seven-piece-or-fewer positions are 100% accurate by definition — they represent exhaustive perfect play.

Can I analyze positions from Chess.com or Lichess?

Yes. Copy the FEN string from those platforms and paste it into the FEN input field. On Chess.com, open any game, right-click the board, and select "Copy FEN". On Lichess, open a game and use the Share menu to copy the FEN. You can also copy FEN from any chess database or PGN file. Once pasted, the board loads instantly and you can find the best move at your preferred depth.

Does the chess calculator work on mobile?

Yes. The web app is fully optimized for mobile devices including smartphones and tablets. The board uses touch drag-and-drop so you can place pieces with your finger. The layout adapts to narrow screens. The computation runs in a background Web Worker thread so the UI stays responsive while the engine is calculating. It works on Chrome, Firefox, and Safari for iOS and Android — no app download required.

What is the difference between this calculator and the Chess Game Analyzer?

They serve two different purposes. This Chess Calculator is for analyzing a single position instantly — paste a FEN, choose your depth, and get the engine's best move and evaluation for that one position in seconds. The Chess Game Analyzer is for reviewing a complete game after you've played it — it loads a full PGN or imports games by your Chess.com or Lichess username, then scores every move by centipawn loss, flags all blunders and inaccuracies, and produces an accuracy report. Use this calculator when you're stuck on one position; use the Game Analyzer for a full post-game review.

Want a Full Game Review?

This calculator finds the optimal move for a single position. For a complete post-game analysis — including move-by-move scoring, an accuracy report, and opening detection — use the Chess Game Analyzer.

Free · No sign-up · Import PGN or load by username

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