Tool · Calculator
Expected value (EV) calculator
A bet is worth making when the odds pay more than your true probability implies. Enter your estimated win probability, the decimal odds on offer, and your stake — we'll show your expected value, ROI, the fair break-even odds, and your edge.
Expected value
+$10.00
Positive EV (+10.0% edge). The odds are better than your estimated probability implies.
ROI per bet
10.00%
Fair (break-even) odds
1.82
Edge vs price
+10.0%
How it works
- EV formula: stake × (probability × decimal odds − 1). Positive = the price beats your probability.
- Fair odds: 1 / your probability. If the offered odds are higher than fair, you have an edge.
- Where to get a probability: prediction markets give a live, money-weighted estimate — a useful sanity check against your own. See the Odds Desk.