Calculate expected value
Every EV calculator betting workflow starts the same way: it compares the market's implied probability with an independent probability estimate, so the output is only as reliable as the estimate you enter. This is also a value betting calculator, priced in edge and expected value rather than a bare yes or no.
Formula and worked example
Expected value per unit = (Estimated probability x Decimal odds) - 1
Expected ROI = Expected value per unit x 100%
Expected profit = Stake x Expected value per unit
Edge = Estimated probability - Implied probability
At odds of 1.95 and an estimated probability of 53.8462%, expected value is about +0.05 per unit, an expected ROI of about +5%. A stake of 20 therefore has an expected profit of about 1 under those inputs. This is a probability-weighted expectation, not the next result.
Interpreting edge and expected value
A positive result means your estimate is higher than the market-implied probability by enough to overcome the price. A negative result means the offered price is below the fair price implied by your estimate.
Review how you produced the estimate, account for market margin and track whether your assumptions remain calibrated. The vig calculator can normalise a full market before comparison.
Limits and responsible use
Expected value does not guarantee profit. Limits, price movement and operator settlement rules can change the available or realised result. See Gambling Commission LCCP 4.2.6.
Set a spending limit before gambling and do not chase losses. Read GambleAware's advice and our responsible gambling guidance.
Related tools and guides
After checking the price and risk, you can compare betting partners. Oddly Likely may earn a commission from partner links; check current odds, eligibility and terms. Read the affiliate disclosure.
Frequently asked questions
How do you calculate expected value on a bet?
Expected value per unit = (your estimated probability x decimal odds) - 1. Multiply by your stake for expected profit. A 55% estimate at 2.00 decimal (+100 moneyline) gives (0.55 x 2.00) - 1 = 0.10, or 10p expected profit per pound staked.
What is a positive EV bet?
One where your estimated probability of winning is higher than the probability the price implies. Positive expected value describes the relationship between your estimate and the price. It does not mean the bet is likely to win.
What is the edge in betting?
The gap between your estimated probability and the implied probability of the price. If you make an outcome 55% and the price implies 50%, your edge is five percentage points.
Where does the probability estimate come from?
You supply it. This calculator does not generate a probability, and Oddly Likely does not publish one for you to paste in. The output is only as good as the estimate you enter, which is why the counterargument on our market pages matters.
Sources
- Gambling Commission, LCCP condition 4.2.6. Current code accessed 30 July 2026.
- GambleAware, Advice to consider if you're gambling. Accessed 30 July 2026.