Investing

Kelly Calculator

Explore Kelly-based stake estimates and bankroll risk under explicit assumptions

Stake Estimate
Use an explicit probability or a tipster's canonical bankroll and ROI. This is read-only and does not place a bet.
Estimate Result
Kelly-based sizing and price-specific value under the submitted assumptions
Enter assumptions and estimate a stake to see the calculation.
Comparison assumptions
Compare five staking policies on exactly the same simulated tips.

Alternative stakes

Costs

Comparison only. It never changes live staking settings.

Risk comparison
Run the comparison to see median bankroll paths and tail risk.
Five methods, one shared set of seeded outcomes.
Simulator Parameters
Simulate expected cashflow using your actual Kelly settings

Historical or expected ROI of the tipster

Compares 100%, 50%, or 25% of the saved Kelly-based stake estimate. This doesn't change your live settings.

Reuse the same seed and inputs to reproduce the exact run.

Costs

Subscription or fixed costs deducted monthly

Cashflow Projection
Configure parameters and run the simulation
Click "Run Simulation" to generate bankroll projections
Loading live sizing policy...
How Kelly Criterion Works

The Kelly Formula

The Kelly Criterion estimates a growth-maximizing fraction of your bankroll to stake on each bet under a specific probability model. The standard formula is f* = (bp - q) / b where b = net odds (decimal odds - 1), p = win probability, and q = loss probability (1 - p).

Our Implementation

This system uses a modified Kelly approach designed for tipster-based betting. Instead of estimating win probability directly, we derive it from the tipster's historical ROI and advised odds: p = (1 + ROI) / advisedOdds. This makes the calculation grounded in actual performance data.

Safety Mechanisms

  • Kelly Reduction: Divides the raw Kelly fraction by a configurable factor (default 3x) for more conservative sizing. This reduces volatility at the cost of slower growth.
  • Kelly Cap: Hard maximum on stake as a percentage of bankroll (default 10%), preventing over-exposure on any single bet.
  • Max Odds Improvement: Limits the benefit when actual bookmaker odds are better than advised odds, preventing over-staking on potentially mispriced opportunities.
  • Edge Validation: Rejects calculations where edge exceeds a threshold (default 60%), flagging likely data errors.
  • Minimum Placed Stake: A bet that carries edge is placed at no less than 30 DKK per ticket, and rounded to a whole unit of the bookmaker's currency. Sizing itself is never raised — the floor is applied when the bet is placed, so a small Kelly fraction is lifted rather than skipped.

How This Differs From Standard Kelly

  • Uses unit-based edge calculation from tipster ROI instead of estimated win probability
  • Supports variable unit strategies where ROI scales with confidence level
  • Limits benefit from odds improvements (standard Kelly would increase stake proportionally)
  • Never increases the final fraction above raw/full Kelly, including at long odds