{"uid":"cap_ocq5idtlZ8gorbJX9pZMl","slug":"portfolio-stats-kelly-criterion-calculator-34785898","name":"Portfolio Stats – Kelly Criterion Calculator","description":"Kelly criterion fraction for a stated win probability and payoff, with growth rate and overbet threshold. NOT advice.","url":"https://portfolio-stats.x402tookit.com/kelly?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["p","b"],"properties":{"a":{"type":"number","description":"Loss on a loss as a fraction of the stake, above 0 and at most 1 (default 1 = lose the whole stake)"},"b":{"type":"number","description":"Gain on a win as a fraction of the stake (1 = even money, 2 = win twice the stake)"},"p":{"type":"number","description":"Win probability you state, between 0 and 1 (exclusive)"},"fractionOfKelly":{"type":"number","description":"Optional multiple of full Kelly to also report, above 0 and at most 1 (0.5 = half Kelly)"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"source":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"fullKelly":{"type":["null","number"]},"halfKelly":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"formulaValue":{"type":["null","number"]},"gainFraction":{"type":["null","number"]},"lossFraction":{"type":["null","number"]},"winProbability":{"type":["null","number"]},"educationalOnly":{"type":["null","string"]},"growthRateAtKelly":{"type":["null","number"]},"growthRateAtHalfKelly":{"type":["null","number"]},"overbetThresholdStake":{"type":["null","number"]},"oddsBreakEvenProbability":{"type":["null","number"]},"expectedValuePerUnitStaked":{"type":["null","number"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_MWfjHSm8Q9QjvBcsE28Iu","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Computes the Kelly criterion optimal bet fraction, growth rate, and overbet threshold for a given win probability and payoff ratio","exampleAgentPrompt":"What's the Kelly criterion fraction I should bet if my win probability is 0.60 and I win twice my stake on a win but lose the whole stake on a loss? Also show me the half-Kelly.","exampleUseCases":[{"title":"Sports betting bankroll sizing","prompt":"I think there's a 65% chance my team wins and the bookmaker is offering 1.8x my stake on a win. What fraction of my bankroll does Kelly say I should bet, and what's the overbet threshold where I'd be hurting my long-run growth?"},{"title":"Trading strategy position sizing","prompt":"My backtested strategy wins 55% of the time and the average win is 2.5x the average loss. Can you run the Kelly criterion calculation so I know the optimal fraction of capital to allocate, plus the expected growth rate at full and half Kelly?"},{"title":"Expected value sanity check on a wager","prompt":"Before I place this bet, can you calculate the break-even win probability and expected value per unit staked for a 58% stated win probability with a 1-to-1 even money payoff? I want to know if the edge is real."}],"resultDescription":"Returns the full Kelly fraction (optimal bet as a proportion of bankroll), an optional specified fraction of Kelly (e.g. half-Kelly), the log growth rate at Kelly and at half-Kelly, the overbet threshold stake beyond which growth turns negative, the break-even (odds) probability, expected value per unit staked, plus input echo fields (win probability, gain fraction, loss fraction) and a mandatory educational disclaimer.","failureModes":["Missing required query param p (win probability) or b (gain fraction) returns an error","p outside (0,1) exclusive range returns a validation error","b at or below 0 returns a validation error","a (loss fraction) outside (0,1] returns a validation error","fractionOfKelly outside (0,1] returns a validation error","Negative expected value inputs (Kelly would be zero or negative) may return zero or a specific note","Payment failure or insufficient USDC balance returns HTTP 402"],"whenToPreferThis":"Use this endpoint when you need a precise, formula-driven Kelly criterion calculation with educational framing — including growth rate and overbet threshold — rather than a generic probability calculator. Prefer it over manual computation when you need the full suite of Kelly outputs (full Kelly, fractional Kelly, growth rate, overbet threshold, break-even probability, EV) in a single call. It is part of a coherent portfolio-stats toolkit so it pairs naturally with sibling endpoints for volatility, Sharpe, drawdown, and return series analysis.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-29T13:14:28.245Z","isFirstParty":false,"canonicalSlug":"portfolio-stats-kelly-criterion-calculator-34785898"}