Model full, half, and fractional Kelly allocations precisely. Compare stake sizes, growth rates, and safety. Turn edge estimates into smarter portfolio sizing choices today.
The page stays in a single-column flow, while the form uses three columns on large screens, two on smaller screens, and one on mobile.
These examples are illustrative and help users understand how the inputs change the Kelly fraction.
| Scenario | Win % | Gain % | Loss % | Cost % | Payoff Ratio | Full Kelly % | Half Kelly % |
|---|---|---|---|---|---|---|---|
| Balanced trend setup | 55 | 12.0 | 6.0 | 0.5 | 1.7692 | 29.57 | 14.79 |
| Steady swing trade | 60 | 10.0 | 8.0 | 0.25 | 1.1818 | 26.15 | 13.08 |
| Lower hit, bigger upside | 45 | 18.0 | 7.0 | 0.5 | 2.3333 | 21.43 | 10.71 |
| Weak edge example | 48 | 9.0 | 10.0 | 0.5 | 0.8095 | -16.23 | 0.00 |
1) Adjusted gain = Average gain − Costs
2) Adjusted loss = Average loss + Costs
3) Payoff ratio = Adjusted gain ÷ Adjusted loss
4) Adjusted probability = 0.50 + (Raw probability − 0.50) × (1 − Haircut)
5) Loss probability = 1 − Adjusted probability
6) Full Kelly fraction = ((b × p) − q) ÷ b
7) Applied Kelly fraction = min(Full Kelly × Multiplier, Position Cap)
8) Suggested position amount = Account capital × Applied Kelly fraction
Here, b is the payoff ratio, p is adjusted win probability, and q is adjusted loss probability. This version is practical for investing workflows where you estimate average gains, average losses, and trading costs.
It estimates the fraction of capital to allocate when you know the probability of winning and the payoff relationship between gains and losses.
Fractional Kelly reduces volatility and softens the effect of estimation errors. Many investors prefer half Kelly or quarter Kelly rather than the full theoretical fraction.
Costs reduce effective upside and increase effective downside. Ignoring them can overstate your edge and push the recommended position size too high.
It pulls the win probability closer to 50%. This is useful when your backtest sample is small or you are less certain about your real trading edge.
A negative output means the adjusted edge is unfavorable. In that case, the calculator suggests no position because the trade does not justify risk.
Even a valid Kelly estimate can be too aggressive in real markets. A cap limits concentration risk, liquidity problems, and errors in your assumptions.
No. It helps with single-strategy sizing, but portfolio correlation, diversification, leverage rules, and drawdown limits still need separate analysis.
No. This tool is educational. Use it as a sizing framework, then combine it with risk controls, research, and your own judgment.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.