How the Expected Value (EV) Calculator Works
The Betstamp Expected Value Calculator measures whether a bet is mathematically profitable in the long run. Enter the sportsbook's odds, your estimated win probability, the true (fair) odds, and your bet amount — the calculator returns the expected value as a percentage and the expected profit in dollars.
How to Use the EV Calculator
- Enter the Odds offered by the sportsbook (e.g., –110)
- Enter your estimated Win Probability as a percentage (e.g., 55)
- Enter the True Odds (typically derived from a sharp book's devigged line)
- Enter your Bet Amount (e.g., $100)
- The calculator returns:
- Expected Value %: your mathematical edge as a percentage
- Expected Profit: your expected return in dollars on the wager
Tip: Using both Win Probability and True Odds as separate inputs lets you cross-check your probability estimate against the actual devigged price. They should line up closely. If they don't, your estimate is off — or the True Odds source is soft.
What is Expected Value (EV) in Sports Betting?
Expected value is the average amount a bet will return if placed repeatedly under identical conditions. It's calculated as:
EV = (Win Probability × Profit if Win) – (Loss Probability × Amount Lost)
A +EV bet has a positive expected dollar return. A -EV bet has a negative expected return. Everything else — gut feel, recent results, vibe — is noise.
Worked example: Bet $100 on the Maple Leafs at +120. You estimate the fair win probability at 50% (based on a sharp book's devigged line).
- Win: 0.50 × $120 = $60
- Loss: 0.50 × $100 = $50
- EV = +$10
Every time you place this bet, you expect to earn $10 on average over a large sample.
How to Calculate Expected Value on Any Bet
To calculate EV accurately, you need:
- The sportsbook's odds (what's being offered)
- Your best estimate of true win probability
- Optionally, a second reference — true odds from a sharp sportsbook
The EV Calculator takes all three. The most accurate true-probability estimates come from devigging a sharp book's lines using the Betstamp No-Vig Fair Odds Calculator and plugging the result into this calculator.
Why Positive EV (+EV) Betting Matters
+EV betting is the only mathematically proven long-term winning strategy in sports betting. Every professional bettor places bets where their estimated true win probability is higher than what the sportsbook's odds imply.
Over a small sample, +EV bets lose constantly — variance is real. Over thousands of bets, +EV produces consistent profit. Your win rate might only be 54%, but if each bet carries a real edge, those edges compound.
Most recreational bettors lose because they place -EV bets: correlated parlays, high-vig props, "feel" bets. Professionals win because they only place +EV bets and size them using the Kelly Criterion.
How Betstamp PRO Automates +EV Betting
Calculating EV manually on every bet is impossible at scale. Betstamp PRO pulls live odds from 20+ major sportsbooks, devigs sharp-book lines, compares them against softer books in real time, and surfaces every +EV bet as it appears.
Instead of running one EV calculation at a time, you get a live feed of every +EV opportunity currently in the market.
Pairing EV With Kelly Criterion for Bet Sizing
Once you know a bet is +EV, the next question is: how much should you bet? The Betstamp Kelly Calculator uses your edge (derived from EV) to calculate the optimal stake. Most sharp bettors use a fractional Kelly approach (¼ or ½ Kelly) to reduce variance — which Betstamp's Kelly Calculator supports directly via the Kelly Multiplier input.
With Betstamp PRO—the most advanced top-down betting odds screen in the market. Bettors will find hundreds of daily betting edges with ease, allowing you to scale your profits long-term. Click the banner to book a free demo.
