# The Chess Calculator > Free chess tools that stay quiet until you ask. Stockfish 18 runs in your browser tab, so a position you paste is never uploaded. The Chess Calculator is a set of single-answer chess tools built around one rule: your move first, ours when you ask. Nothing runs when a page loads. The visitor sets up the position, thinks it through, and asks for help when they want a second opinion. Then the answer is the largest thing on the page, followed by one sentence on why. There is no account, no paid tier, and no server-side analysis. ## The rule every tool follows 1. The engine loads in the background, but it does not search until the visitor asks. 2. No arrows, no eval bar, and no answer on a position the visitor has not asked about. 3. Once asked, the answer is the largest thing on the page, followed by one sentence on why. 4. Nothing pasted leaves the tab. No account, no daily cap, no ads. 5. Bad input is named, not silently repaired into a different position. 6. Not for live games. Using an engine during a rated game is cheating. The tools are for after the game and for study positions. ## Tools available today ### Best move calculator For when a person is stuck on one position. Paste a FEN, a PGN, or a public Chess.com or Lichess game link, or set the pieces on the board. Nothing is evaluated while the position is being built. On Find best move, the page returns the best move, the evaluation, two alternative moves, and a short plain-language reason the engine likes the move it picked. Open it at . ### Best move in algebraic chess notation For rule 16 of The Password Game. The board starts empty with a piece palette, so the diagram the game shows can be rebuilt in about a minute. Pick White or Black to move and the page returns the one move to paste, written like Qd5+, and says whether the position is the checkmate in two the game always uses. Open it at . ### Pathwise For when a person wants to find the move themselves first. They play a move on one board. The engine plays its move on a second board only after they commit, and a plain-language note explains the difference. Moves are permanent, with no undo, so they play on from the position they created. Open it at . ## Tools coming soon ### Rating converter For when a rating needs to make sense in another system. Converts between Chess.com, Lichess, USCF, and FIDE rating points, with the method and the date the table was last updated printed on the page. ## How the engine runs Stockfish 18 Lite with its NNUE network is compiled to WebAssembly and served from this domain. It is downloaded once, then evaluated inside the browser tab. When the browser grants cross-origin isolation the multi-threaded build runs; when it does not, the single-threaded build runs instead. Either way the search reaches depth 18 and reports three candidate moves. Because the engine is client side, there is no HTTP endpoint that returns an evaluation. An agent that needs an answer should send the person to the calculator with their FEN. ## Input the calculator accepts - FEN, including partial FENs that name a clear position - PGN, from which the final position is taken - A public Chess.com game link - A public Lichess game link - Pieces placed by hand on the board Illegal or ambiguous input is named as such. The page does not silently rewrite a broken FEN into a different position. ## Privacy Positions, FENs, and engine output stay in the tab. Game imports fetch the public PGN from Chess.com or Lichess so the engine can run locally, and no copy is kept. Full detail is at . ## Pages - [Best move calculator](https://thechesscalculator.com/best-move-calculator) - [Best move in algebraic chess notation](https://thechesscalculator.com/best-move-in-algebraic-chess-notation) - [Pathwise](https://thechesscalculator.com/pathwise) - [About](https://thechesscalculator.com/about) - [Contact](https://thechesscalculator.com/contact) - [Privacy](https://thechesscalculator.com/privacy) - [Agent instructions](https://thechesscalculator.com/llms.txt)