Updated: 2026-02-20
Estimate a Kelly fraction from win probability and win/loss ratio to size risk without overbetting. The calculator is free and intentionally simple so you can plan trades quickly without skipping risk logic.
$ tool
Estimate a Kelly fraction from win probability and win/loss ratio to size risk without overbetting.
Note
Outputs are only as accurate as your inputs.
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$ kelly
15% bankroll
Enter your inputs before you place the trade, not after. Pre-trade planning is where calculators create value.
Use realistic values based on your actual execution conditions. If you understate slippage, fees, or stop distance, output quality collapses.
Document the result inside your journal so you can compare planned vs realized outcomes during review.
Kelly sizing maximizes long-run growth under assumptions, but it is extremely sensitive to estimation error.
Most traders should use fractional Kelly (e.g. 0.25–0.5) as a guardrail against overbetting.
Most preventable losses come from skipping one simple calculation when markets move fast. This tool enforces the minimum math needed for disciplined execution.
The value compounds when used consistently. One correct risk decision rarely changes a year; repeated correct decisions usually do.
Tie calculator output to your strategy tags so you can evaluate whether your planning assumptions match live performance.
Use this tool at planning time, then compare outcome quality in weekly review sessions.
If planned and realized values diverge, investigate execution behavior before adjusting strategy logic.
Pair this with one behavior correction each week for compounding improvement.
Using unrealistic inputs because they feel better emotionally.
Changing parameters mid-trade to justify staying in a bad position.
Treating one output as a signal to trade rather than a risk filter.
Yes. The calculator is free and available without signup.
Kelly estimates an optimal fraction of capital to risk when you know win probability and payoff ratio. It maximizes long-run growth in theory, but it is highly sensitive to estimation error.
Usually no. Full Kelly can produce severe drawdowns if your inputs are wrong or markets change. Many traders use fractional Kelly (like 0.25x to 0.5x) as a conservative risk cap.
Outputs are only as accurate as inputs. Use realistic assumptions and review planned vs realized values weekly.
Yes. You can pair tool outputs with your review workflow and setup tags for better post-trade diagnostics.
See plans and run one weekly review loop with Tiltless: edges, leaks, and enforceable next actions.
