Value Bet / EV Calculator
Check whether the odds on offer are longer than your own view of the outcome justifies.
Value Bet / EV Calculator
Compare your own estimate of an outcome against the price to see whether the bet is worth making.
Your own estimate of the outcome
Implied by odds
40.00 %
Your estimate
45.00 %
Edge
12.50 %
Expected value
+₦125.00
Expected value is an average over many identical bets, not a prediction about this one. A +EV bet still loses most of the time at long odds.
What is a Value Bet?
A value bet is one where the price is longer than the true chance warrants. It has nothing to do with whether the bet wins — a value bet can lose, and a bad bet can win. Over a long run only the gap between your estimate and the price decides whether you finish ahead.
The Formula
- Expected value: EV = (P × (O − 1) × S) − ((1 − P) × S)
- Which simplifies to: EV = S × (P × O − 1)
- Value exists when P × O > 1
- Edge: (P × O − 1) × 100 %
The two forms are the same statement — the first tracks the win and loss cases separately, the second collapses them. The second is easier to hold in your head at the bet slip.
Example
A team is priced at 2.50, implying 40 %. Your own read is 45 %, and you are staking ₦1,000.
- P × O = 0.45 × 2.50 = 1.125
- Edge: 12.5 %
- EV: ₦1,000 × 0.125 = +₦125 per bet on average
That ₦125 is an average across many such bets. This particular one wins 45 % of the time and returns ₦2,500 when it does; the rest of the time it returns nothing.
Where the Probability Comes From
This is the entire difficulty, and no calculator can help with it. Workable sources:
- A no-vig line from a sharper book. Strip the margin from a low-margin bookmaker and use that as the fair probability, then look for a longer price elsewhere.
- Closing prices. The price just before kick-off is the market's best estimate; beating it consistently is the standard test of a genuine edge.
- Your own model. Base rates, expected goals, injuries — anything the price may not have absorbed yet.
What does not work is converting the same bookmaker's price back into a probability and nudging it to taste. That produces value on demand and none in reality.
Frequently Asked Questions
How do I know a bet has value?
When your estimate of the chance beats the chance the price implies — in one line, when P × O > 1. A price of 2.50 implies 40 %; if you rate the outcome at 45 %, the bet is +EV by 12.5 %. Everything else is bookkeeping.
Where does my probability come from?
From something independent of the price you are judging. A model, long-run base rates, or the no-vig price at a sharper bookmaker are all defensible. What does not work is converting the same bookmaker’s odds back into a probability — that guarantees no value by construction.
Does positive EV mean I will win this bet?
No. EV is the average across many identical bets, not a forecast of one. A +EV bet at 5.00 still loses about four times in five. Value betting only pays out over a large sample, which is why stake sizing matters as much as selection.
How much edge is worth betting?
Anything genuinely positive is worth taking, but small edges are easily imaginary. A 1–2 % edge sits inside the error of most people’s estimates; 5 % and above is where a real advantage usually shows. Bear in mind that a bookmaker margin of 5 % has to be overcome before your edge starts at zero.
Related Tools
- No-Vig Calculator — derive a fair probability from a sharper market to compare against.
- Kelly Criterion Calculator — once there is an edge, this sizes the stake.
- Implied Probability Calculator — the percentage a price is claiming, per outcome.