Kelly, honestly
Kelly sizes a bet from an edge you already have; it cannot create one. If your probability does not beat the price’s break-even chance, the stake is zero. Overestimating your chance can turn a confident stake into a costly mistake.
Kelly is a staking rule too — unlike the progressions it needs a real edge, which the price rarely leaves you.
Price-implied break-even probability: 50.00%.
With no edge Kelly bets nothing: your probability is no higher than the price-implied break-even chance.
| Sizing | Fraction of bank | Initial stake | Chance of halving within 100 bets |
|---|---|---|---|
| Full Kelly | 0.00% | 0.00 | 0.00% |
| Half Kelly | 0.00% | 0.00 | 0.00% |
Estimated market probability after proportional margin removal: 46.94%. This is an approximation of what the market thinks, using the overall typical margin, not a price-specific estimate.
The market average is the overround of the averaged prices, which is lower than the margin of a typical single bookmaker.
If your number is the market’s, Kelly says 0.
Source: bookmaker_margins, market-average closing triplets; 62,016 priced matches, season start years 2021–2025, computed 2026-09-30 08:58:39 by football:index:bookmaker-margins (BookmakerMarginIndexer).
Five complete seasons per calendar: split-year editions are treated as complete after June 30, calendar-year editions after December 31; only recognised dated seasons and played matches. No opening-price fallback.
Method
With decimal odds o and your chance p as a fraction, full Kelly f = max(0, (o × p − 1)/(o − 1)); stake = bank × f. Half Kelly uses f/2. Estimated market chance = 1/[o × (1 + typical overround)]. Risk is calculated server-side by an exact absorbing binomial recursion, not simulation: at every bet, paths reaching 50% of the initial bank or less are counted once. Stakes resize as a fixed fraction of the remaining bank; all 100 bets are independent with the same odds and your stated true probability. Risk assumes a positive starting bank.
What this does not claim: your probability is accurate, that the historical average margin applies to this price, or that any stake is safe. Rounded zero risk is not a guarantee; probability error and correlated bets invalidate the risk estimate.
Not betting advice