General Betting Math
Kelly Criterion Calculator
Use this page to test full Kelly stake for a precisely defined betting calculation. Recalculate when the event, period, price, or settlement rule changes.
Define the market and its inputs
These defaults are a calculation example. Current market information must be supplied by the user.
What is being estimated
Size a wager from bankroll, price, and estimated edge. Read full Kelly stake within the event period entered here, because another betting calculation may settle differently; save the source beside the revised output.
Use the price offered for the exact selection rather than an earlier screenshot or a price from another sportsbook. Settlement and data scope matter here because stake sizing is highly sensitive to an overstated edge; probability error is a bankroll risk, not a rounding issue.
Input definitions and source checks
- Bankroll opens this full Kelly stake case; current betting bankroll; label it as observed, quoted, or projected.
- For full Kelly stake, enter Estimated win probability on the printed basis because your probability estimate; retain the original precision.
- The Kelly Criterion Calculator uses American odds as a later input; enter positive or negative American odds; note when it was current.
The event snapshot is stale when a price move changes the economics even when the event assumptions stay the same; recheck the compared market as well.
Worked example with independent values
For the Kelly Criterion Calculator, the sample changes the starting values so the calculation can be followed without implying that the numbers are representative.
- Bankroll: $910
- Estimated win probability: 57.75%
- American odds: -125
Applying the Kelly Criterion rule: Kelly fraction = (decimal odds × probability − 1) ÷ (decimal odds − 1).
| Full Kelly fraction | 4.94% |
|---|---|
| Applied fraction | 100.00% |
| Estimated edge | 3.95% |
For this full Kelly stake example, recalculate the example after any code or formula change so the page retains a visible arithmetic check.
From the entered values to the result
For the Kelly Criterion Calculator, the Kelly fraction compares entered win probability with the break-even rate in the odds and scales the bankroll by that edge.
One explicit Kelly Criterion Calculator assumption is Bankroll, defined here as: current betting bankroll.
Preserve the precision supplied by the source during calculation, then round the reported answer only when presenting it; verify the settlement basis before reading the difference.
A bettor comparing this output with fractional kelly can open the Fractional Kelly and keep the assumptions distinct.
Before acting on the number
Kelly staking can be highly volatile when the probability estimate is wrong.
Confirm the posted price, promotion restrictions, maximum stake, push treatment, and void policy.
Interpret the Kelly Criterion Calculator result only after checking that stake sizing is highly sensitive to an overstated edge; probability error is a bankroll risk, not a rounding issue.
For dutching, use the Dutching after saving the inputs behind full Kelly stake.
Preserve the market snapshot
Keep the market name, compared price, and calculation time beside full Kelly stake; record when “Estimated win probability” was current and whether it was measured or estimated.
Update the Kelly Criterion Calculator if “Bankroll” changes enough to affect the comparison; do not use extra decimal places as a substitute for uncertainty.
Using this result correctly
Does this page retrieve live odds?
No. The Kelly Criterion Calculator calculates only from user-entered values.
Where should bankroll come from?
Current betting bankroll. Match its event and period to the other fields.
Can this result be compared with another period?
Not directly; the Kelly Criterion Calculator inputs and line must cover the same period.
How can sensitivity be tested clearly?
Keep the first result, change one uncertain field, and calculate again.
What does full Kelly stake represent here?
Full Kelly stake follows Kelly fraction = (decimal odds × probability − 1) ÷ (decimal odds − 1); it contains no unlisted news or prices.