# Chess FEN, PGN & Elo Rating Tutor Parse & validate FEN board snapshots, PGN/SAN movetext (with parity, check/mate counts, threefold); compute Elo rating updates from win/draw/loss results, with Lichess/Chess.com tier bands > Canonical page: https://elysiatools.com/en/tools/chess-fen-pgn-elo-rating-tutor - **Category:** Games & Entertainment - **Keywords:** chess, fen, pgn, san, elo, rating, lichess, chess.com, glicko, opening, notation ## Overview For chess beginners, game-analysis students, and Chess.com/Lichess players. FEN mode: parses the 6 fields, validates 8 files per rank, one king per side, non-adjacent kings, no pawns on ranks 1/8, and renders the board. PGN mode: strips comments/variations/NAGs, validates each SAN move structurally, counts plies, and tallies checks / checkmates / castles. Elo mode: applies the standard formula E = 1/(1+10^((Ropp−R)/400)) and R' = R + K·(ΣS − ΣE) with opponents held at pre-event ratings (K=32 amateur default), plus Lichess/Chess.com community tier bands. Pure local, deterministic. ## Inputs - **Mode** (select) - **FEN** (textarea): FEN string, e.g. rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 - **PGN movetext** (textarea): PGN movetext, e.g. 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 1/2-1/2 - **Player rating** (number): e.g. 1613 - **K-factor** (number) - **Games (opponent rating, result)** (textarea): One per line: opponentRating then result. 1609 loss 1477 win 1388 win 1586 win 1720 loss ## When to use - Validate a FEN string and inspect the resulting chessboard position. - Check PGN or SAN movetext for structural issues and review move statistics. - Estimate a new Elo rating after a series of wins, draws, or losses. ## How it works - Choose FEN analysis, PGN analysis, or Elo calculation from the mode selector. - Enter a FEN string, PGN movetext, or player rating with one opponent rating and result per line. - For Elo calculations, set the K-factor if needed; the default is 32. - Review the HTML result, including validation details, board or move statistics, rating projections, and applicable tier information. ## Use cases - Chess students can verify starting positions, custom FEN snapshots, and legal board structure. - Game analysts can inspect SAN notation, move counts, checks, checkmates, castles, and results in a PGN. - Tournament players can project rating changes from a multi-game record using a chosen K-factor. ## Frequently asked questions ### What does FEN analysis validate? It parses the six FEN fields and checks board structure, including eight files per rank, one king per side, non-adjacent kings, and no pawns on the first or eighth rank. ### What can PGN analysis detect? It removes comments, variations, and NAGs, validates SAN move structure, counts plies, and tallies checks, checkmates, castles, and the game result. ### How is the Elo update calculated? It uses the standard expected-score formula and applies R' = R + K·(ΣS − ΣE), with opponent ratings fixed at their pre-event values. ### What is the default K-factor? The default K-factor is 32, and it can be changed from 1 to 60. ### Are the Lichess and Chess.com tiers official? No. The tier bands are community estimates; Lichess uses Glicko-2 and Chess.com uses Glicko-1 rather than standard Elo. ## Related tools - [JSON Key Extractor](https://elysiatools.com/en/tools/json-key-extractor): Extract all keys from JSON objects with multiple output formats. 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