How to use this betting tool
- Enter the requested assumptions using the units shown.
- Check that probability, odds, stake, line, or outcome values match your intended market.
- Select Calculate, then read the main result and its stated assumption.
#013 · Bankroll & Risk Management Tool
Fractional Kelly Calculator
Scale the Kelly criterion to a chosen fraction of the full theoretical stake. Results depend entirely on your probability estimate.
Calculator
Bankroll and edgeunits
x
%
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What this tool calculates
Scale the Kelly criterion to a chosen fraction of the full theoretical stake. Results depend entirely on your probability estimate.
Full Kelly fraction = (b × p − q) ÷ b, where b = decimal odds − 1, p = win probability, and q = 1 − p.
Results are informational. Actual limits, deductions, voids and settlement can vary by operator and jurisdiction.
Worked example
With a 1,000-unit bankroll, 2.20 odds and a 50% estimate, full Kelly is 8.33%; half Kelly stakes about 41.67 units.
| Input or result | Value |
|---|---|
| Bankroll | 1,000 units |
| Full Kelly | 8.33% |
| Half Kelly stake | 41.67 units |
Tips and limitations
- Use estimates from one consistent source and market definition.
- Do not confuse total return with net profit.
- Recalculate if any input or settlement assumption changes.
- Real betting involves loss risk; a calculator cannot remove it.
FAQ
What formula does the Fractional Kelly Calculator use?
Full Kelly fraction = (b × p − q) ÷ b, where b = decimal odds − 1, p = win probability, and q = 1 − p.
Are the displayed results bookmaker odds or fair estimates?
They are arithmetic results from your inputs. They do not retrieve live prices or add a bookmaker margin.
When does rounding happen?
The calculator keeps full JavaScript numeric precision during calculation and rounds only the displayed values.
Can operator settlement rules change the result?
Yes. Voids, deductions, dead heats, correlated markets and house rules may change real settlement where relevant.
Does this result predict a winning bet?
No. It explains betting mathematics from entered assumptions and does not predict an event or guarantee a return.
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Calculation reference
| Item | Definition |
|---|---|
| Main output | Suggested stake |
| Method | Browser-only arithmetic |
| Live data | Not used |
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