What is expected value in betting?

Expected value (EV) is the average amount you expect to win or lose per bet if you repeated the same bet indefinitely. A +EV bet means you have a long-run edge; a -EV bet means the bookmaker profits over time.

How is EV calculated?

EV = (probability of winning × net profit) − (probability of losing × stake). For example, a 50% chance to win $110 on a $100 bet gives EV = (0.5 × 110) − (0.5 × 100) = $5.

What is a good EV for a bet?

Any positive EV is mathematically favorable. Professional bettors target edges of 2–5% or more. A very high edge (>10%) often indicates an error in your probability estimate rather than a genuine opportunity.

What is the break-even probability?

Break-even probability is the win probability at which EV equals zero. If your estimated win probability exceeds this number, the bet has positive EV; if it is lower, the bet has negative EV.

How do I convert American odds to decimal?

For positive American odds (e.g. +150): decimal = (odds / 100) + 1 = 2.50. For negative American odds (e.g. −110): decimal = (100 / |odds|) + 1 ≈ 1.909. This calculator handles the conversion automatically.

Should I always bet when EV is positive?

Positive EV is a necessary condition for a good bet, but you should also consider your bankroll size, odds variance, and the Kelly criterion to size your bets appropriately.

Expected Value Bet Calculator

Enter your probability estimate, payout odds, and stake to see whether a bet has positive or negative expected value.

Bet Parameters

Win Probability (%)

Your estimated chance the bet wins.

Odds Format

Decimal Odds

Decimal odds include your stake (e.g. 1.91 returns $1.91 per $1 bet).

Stake ($)

Expected Value (EV)

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per bet

Summary

Expected value (EV) is the average outcome of a bet if you were to repeat it many times. A positive EV means the bet is profitable in the long run; a negative EV means the house has an edge. This calculator takes your estimated win probability, the payout odds (in decimal, fractional, or American format), and your stake, then shows your EV, edge percentage, and break-even probability so you can make informed betting decisions.

How it works

Enter your estimated probability of winning as a percentage.
Choose your odds format (decimal, fractional, or American) and enter the odds.
Enter your stake amount.
The calculator computes EV = (P_win × profit) − (P_loss × stake).
Review your EV, betting edge, and break-even probability to decide if the bet is worth placing.

Use cases

Evaluate sports bets to find lines where the bookmaker has mispriced the odds.
Compare multiple bet options side-by-side to pick the highest EV wager.
Check if a parlay or prop bet offers value given your probability estimate.
Practice bankroll management by understanding your edge before placing a bet.
Study poker or blackjack decisions where EV guides optimal play.
Assess daily fantasy sports picks using EV to maximize long-term returns.

Frequently Asked Questions

Last updated: 2026-06-15 · Reviewed by Nham Vu