Quick answer: A value bet is one where your estimated probability of an outcome is higher than the probability the odds imply. This calculator compares the two for you: enter your estimated probability and the decimal odds, and it shows whether the bet has value and how big the edge is as a percentage. Any positive figure means the price is longer than the outcome deserves on your estimate.
What is a value bet?
A value bet has nothing to do with the odds being big or small. It is about a mismatch between two probabilities: the one you believe is true, and the one baked into the price. When your probability is higher than the odds imply, the bet is priced too generously and carries value. When it is lower, the price is too short. Finding value is therefore about the accuracy of your estimate relative to the market, not about backing longshots or favourites.
How value is calculated
Every set of odds contains an implied probability. For decimal odds:
Implied probability = 1 ÷ decimal odds
So odds of 2.50 imply a 40% chance (1 ÷ 2.50). To decide whether a bet has value, compare that with your own estimate using the value formula:
Value = ( your probability × decimal odds ) − 1
A result above zero means value; below zero means none. One refinement matters: the implied probabilities across a market add up to more than 100% because of the bookmaker's margin. Removing that margin first — the "no-vig" price — gives a fairer benchmark and stops you counting the margin itself as value. The no-vig calculator does this.
How to use this calculator
- Enter your estimated probability of the outcome as a percentage — your genuine view of the chance, ideally from a model or the no-vig market price.
- Enter the decimal odds offered on that outcome. Convert fractional or American odds first with the odds converter if needed.
- Read the value figure. The tool shows the implied probability from the odds, your edge as a percentage, and whether the bet clears the value line.
- Sense-check against the no-vig price before trusting a small edge, so you are not mistaking the bookmaker's margin for value.
Worked example
Say you estimate a team's chance of winning at 45% (0.45) and the decimal odds are 2.50.
- Implied probability from the odds = 1 ÷ 2.50 = 40%
- Value = ( 0.45 × 2.50 ) − 1 = 1.125 − 1 = +0.125, or +12.5%
Your 45% estimate is higher than the 40% the odds imply, so the bet has value, with an edge of about 12.5%. If your estimate had instead been 38%, the value figure would be (0.38 × 2.50) − 1 = −0.05, or −5% — no value, because the price is shorter than your own probability. The whole judgement turns on that comparison.
Value bet vs expected value
They are two sides of the same coin. The value figure here tells you whether a bet has an edge and how large it is in percentage terms. Expected value tells you how much that edge is worth in cash for a given stake. A value bet always has positive expected value; use this page to screen for the edge, then the EV calculator to translate it into an amount, and a staking method such as the Kelly criterion to decide how much to risk.
Limitations to keep in mind
- Value is only as reliable as your probability. If your estimate is off, the calculator will still report "value" that is not there. Calibrate against the no-vig price.
- The margin can masquerade as value. Comparing your estimate with the raw odds rather than the no-vig price overstates the edge. Strip the margin first.
- An edge is not a result. Value describes the price, not the outcome. Even a well-judged value bet loses often; the case for it is the long run, not the next match.
Frequently asked questions
How do I know if a bet has value?
Compare your estimated probability with the probability the odds imply (1 ÷ decimal odds). If your probability is higher, the bet has value. The size of the edge is (your probability × decimal odds) − 1.
What is the value betting formula?
Value = (your probability × decimal odds) − 1. A positive result means value; zero means the price is fair on your estimate; negative means no value.
What counts as a good value percentage?
Genuine edges are usually small, so there is no single "good" number. A modest positive figure from a well-calibrated estimate is more meaningful than a large figure from a guess.
Why should I remove the bookmaker margin first?
Raw odds imply probabilities that sum to more than 100% because of the margin. Comparing against those overstates your edge. The no-vig price removes the margin so the comparison is fair.
Is a value bet guaranteed to win?
No. Value describes the price relative to your probability, not the outcome. Value bets lose regularly; the rationale is the average across many bets, not any single one.
Where do I get my probability estimate?
From a prediction model, from the no-vig market price, or from your own analysis. The no-vig market price is a solid neutral benchmark to start from.
Does higher odds mean more value?
No. Value depends only on the gap between your probability and the implied probability. A short-priced favourite can carry value while a longshot does not.
Sources
- Implied probability & bookmaker margin — KiqIQ: implied probability explained
- Value betting method — KiqIQ: value betting explained
For education only. KiqIQ provides probability estimates, not betting advice or guaranteed outcomes. 18+. If gambling stops being fun, support is available at BeGambleAware.org.