Quick answer
Expected value: Expected value is the average result per unit staked if the same bet could be repeated many times; a positive-EV (+EV) price is one above your fair-odds estimate.
Also called: positive expected value, value bet
Explained, with an example
Odds-API.io's formula is EV = fair probability × bookmaker odds − 1, with the fair probability estimated from a panel of sharp bookmakers [1]. Example: fair probability 50% and odds of 2.10 → EV = 0.5 × 2.10 − 1 = +5%. A +EV price says nothing certain about a single result and is only as good as the probability estimate behind it [2]. See Kelly criterion for sizing and Closing line value for checking estimates.
Formula
EV (per unit staked) = fair probability × decimal odds − 1Try it: tools and tutorials
Frequently asked questions
What is expected value?
Expected value is the average result per unit staked if the same bet could be repeated many times; a positive-EV (+EV) price is one above your fair-odds estimate.
About this guide
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Author: Ken Lin · Corrections: if you spot an error, we review it and date-stamp the fix.
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Sources
- Value Bets guide (EV formula, response format, limitations) — Odds-API.io docs, accessed 2 Nov 2026
- What Is Value Betting? Definition & How to Find Value — Odds-API.io glossary, accessed 2 Nov 2026