A flat cash stake remains unchanged. A percentage stake rises or falls with the bankroll entered. Kelly uses an estimated probability and available price to calculate a mathematical fraction, then the tool applies the selected fraction and maximum cap.
| Method | What changes the stake | Main limitation |
|---|---|---|
| Flat cash amount | Nothing until the user changes it | Can become too large relative to a falling bankroll |
| Bankroll percentage | Current illustrative bankroll | Does not consider whether the bet has positive expected value |
| Fractional Kelly | Bankroll, odds and estimated probability | A small probability error can produce a badly overstated stake |
Affordability comes first
No formula can decide what is affordable or make a bet safe. Money needed for bills, savings, debt repayment or emergencies is not a betting bankroll.
Use the expected value calculator to inspect the price and probability assumption separately. The variance calculator shows why a positive estimate can still produce a substantial drawdown.