Expected Value (EV) Calculator

Enter a win probability, a price and a stake to see what a bet is worth on average — and the win rate it needs just to break even.

Win chance (%)Decimal oddsStake ($)

Expected value+9.20%

+$9.20 per $100.00 staked, on average, over many bets.

At $2.10 you break even at 47.6%. This bet needs your 52% estimate to be right — expected value is a statement about the estimate, not a prediction about the result.

The formula

EV% = (probability × decimal odds − 1) × 100

The hard part is not the arithmetic

Every EV calculation depends entirely on the probability you put in, and that number is where all the difficulty lives. Guessing it produces a confident-looking figure built on nothing. The usual disciplined approach is to derive it from a sharp market with the margin removed rather than from an opinion.

What a positive number does and does not mean

It does not mean the bet will win. A +5% bet at $2.10 still loses about half the time.
It is a claim about many repetitions, not about this bet.
If the probability is wrong, the EV figure is wrong by more — it scales with the input.