Kelly Criterion Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-236

Effect

Computation or source lookup only

Input and validation requirements

• Division by zero occurs when b=0; require b>0.
• Require 0≤p≤1; probabilities outside this range are invalid.
• A negative Kelly fraction indicates a negative edge, but the spec does not say whether to display it, clamp the recommended stake to 0%, or interpret it as taking the opposing side.
• The formula can recommend more than 100% of bankroll when the modeled edge is large; leverage, maximum allocation, and shorting constraints are unspecified.
• Estimation error in p and b can materially change the result, so the output should not be presented as a reliable individualized investment or betting recommendation.
• Fees, commissions, spreads, taxes, slippage, ties, partial losses, and correlated positions are not represented.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "win_probability": 0.55,
    "net_odds_b": 1.5
  },
  "expected_outputs": {
    "kelly_fraction_percent": 25,
    "half_kelly_percent": 12.5
  },
  "working": "q=1-p=1-0.55=0.45\nbp=1.5×0.55=0.825\nbp-q=0.825-0.45=0.375\nf*=0.375/1.5=0.25\nKelly percentage=0.25×100=25%\nHalf-Kelly=0.25/2=0.125=12.5%"
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json