Check whether the oddsjustify the risk
Enter the offered odds and your estimated chance of winning. The calculator normalizes the odds, measures expected value, and shows the full-Kelly share of bankroll for a positive edge.
Bet inputs
American (e.g. +150, -110) or decimal (e.g. 2.50)
Implied win probability
Read as decimal odds → decimal 2.5000
Your fair-value chance the bet wins, 0–100
Formula
p = win_probability / 100
b = decimal_odds − 1
EV% = (p × decimal_odds − 1) × 100
Full-Kelly f* = (p × decimal_odds − 1) / (decimal_odds − 1)
American odds are converted to decimal first: +A → 1 + A/100, −A → 1 + 100/|A|. Kelly is shown as 0 when the edge is zero or negative.
The EV% and Kelly fraction above are computed server-side by POST /api/edge — the same endpoint this page calls — so the displayed numbers always match this documented formula.
How to read Kelly
Full-Kelly is aggressive — many traders use half-Kelly instead and stake only 50% of what the formula suggests, balancing growth with lower variance.
Enter valid inputs to see your edge
Odds must be decimal > 1.0 or American (±100 or beyond), and probability between 0 and 100.
Recent calculations
last 5| When | Odds | Win prob | EV | Kelly |
|---|---|---|---|---|
| 2026-09-27 20:31 UTC | 2.50 | 50.00% | +25.00% | +16.67% |
| 2026-09-27 08:01 UTC | 2.50 | 50.00% | +25.00% | +16.67% |
| 2026-09-23 14:26 UTC | 2.50 | 50.00% | +25.00% | +16.67% |
| 2026-09-23 14:25 UTC | 2.50 | 50.00% | +25.00% | +16.67% |
| 2026-09-23 12:40 UTC | 2.50 | 50.00% | +25.00% | +16.67% |
Working from a market share price?
Use the prediction market calculator to compare a YES price with your forecast and turn the result into a bankroll-based stake.