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winningOddsAgainstToEquity

Convert book-style winning odds against back to equity: 1 / (1 + oddsAgainst) for oddsAgainst >= 0. Returns 0 when oddsAgainst is +Infinity.

winningOddsAgainstToEquity(oddsAgainst: number): number

Import​

const poker = require('poker-calculations');

ESM (Node):

import { createRequire } from 'module';
const require = createRequire(import.meta.url);
const poker = require('poker-calculations');

When to use​

Use when the user or a book states odds against (e.g. “4:1 against” → oddsAgainst = 4) and you need equity for comparison to breakevenCallEquity or expectedValueCall.

How to use​

const poker = require('poker-calculations');

const oddsAgainst = 3; // 3:1 against → 25% equity
const equity = poker.winningOddsAgainstToEquity(oddsAgainst);
console.log(equity); // 0.25

// Match equityToWinningOddsAgainst
const again = poker.equityToWinningOddsAgainst(equity);
console.log(again); // 3

// Impossible win line
console.log(poker.winningOddsAgainstToEquity(Number.POSITIVE_INFINITY)); // 0

Returns number — 1 / (1 + oddsAgainst) for non-negative finite oddsAgainst; 0 when oddsAgainst is +Infinity. Throws if oddsAgainst is invalid (negative finite, NaN, etc.).

See also​

equityToWinningOddsAgainst · expectedValueCall · Pot & EV index