Expected Value (EV) Calculator
Put your own probability next to the bookmaker's price and see whether the bet pays over the long run. Positive EV is the only kind of bet worth making.
Value Checker
Enter the price and your win chance to get EV per £1 staked
Accepts decimal (2.50), American (+150, -200), or fractional (5/2) odds
Enter your own probability estimate to calculate expected value
The one number that matters
Expected value is what a bet is worth on average if you could place it thousands of times. Positive means the price is bigger than it should be. Negative means you're paying the bookmaker for the privilege.
EV per £1 = your probability × decimal odds − 1
When your read beats the market
ELO ratings and recent form put the home side at 54%. The best price is 1.95, which implies 51.3%. EV = 0.54 × 1.95 − 1 = +0.053, so every £20 you stake on bets like this earns about £1.06 on average. It won't feel like much. Do it every week and it's the gap between winning and losing.
Value or not?
| Odds | Implied | Your view | EV | Verdict |
|---|---|---|---|---|
| 1.95 | 51.3% | 54% | +5.3% | Back it |
| 3.30 | 30.3% | 28% | −7.6% | Leave it |
| 6.50 | 15.4% | 17% | +10.5% | Back it |
| 1.40 | 71.4% | 70% | −2.0% | Leave it |
| 2.62 | 38.2% | 40% | +4.8% | Back it |
Keep yourself honest
- •Your probability is the weak link. An EV figure is only as good as the chance you typed in. Be strict with yourself.
- •Beat the closing price. If the odds shorten after you bet, your number was probably right. Track your prices against the close.
- •Compare with the fair price. Run the market through the overround calculator first. Your view against the no-vig price shows how far you really disagree with the market.
- •Expect losing runs. That +10.5% bet at 6.50 still loses more than four times in five.
- •Then size it. Once a bet is positive EV, the Kelly calculator tells you how much it deserves.
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