Choose a calculation
Start with the number you have and the decision you need to check. Returns and conversions belong in the odds tool; market-wide probability questions need the vig or arbitrage tools.
Calculate returns and convert odds
Enter a stake and decimal, fractional or American odds to compare formats, profit and potential return.
Convert odds to implied probability
Turn one quoted price into the probability represented by that price.
Measure the margin in a market
Work out the book percentage and overround, and see how much of the price is the bookmaker's cut.
Remove the vig and find fair odds
Strip the margin out and get the fair price behind a moneyline, decimal or fractional market. Handles two to six outcomes, so three-way football works.
Estimate expected value
Compare your probability estimate with offered odds and calculate the resulting edge and expected profit.
Check an arbitrage allocation
Test two to six prices and divide a total stake for an equalised theoretical return.
Size a stake with the Kelly criterion
Turn an edge and bankroll into full, half and quarter Kelly stakes for a single bet.
Price a parlay and its true cost
Combine two to twelve legs for the payout, then see the no-vig true odds and the compounded bookmaker hold.
Build a round robin
See how many parlays a round robin really creates, what it costs in total, and what each combination returns.
Convert a free bet to cash
Work out the lay stake and liability that lock in a stake-not-returned free bet, and the percentage of face value you keep.
Model a football match from expected goals
Turn home and away xG into every scoreline, the home-draw-away split, fair odds, goal totals and both teams to score.
How the tools fit together
Odds formats describe the same price in different ways. Implied probability converts that price into a percentage. A vig calculation then considers every outcome in the same market so the bookmaker margin can be separated from a normalised probability split.
Every tool above starts from a price. The Poisson calculator is the exception: it starts from expected goals and produces the probabilities the others consume, which is why it sits at the end of the list rather than in the conversion chain.
Value and arbitrage answer different questions. Value depends on a probability estimate that you supply. Arbitrage compares available prices across every outcome and checks whether their inverse sum is below 100%.
Read the market as well as the maths
Use the value betting guide to build a price-checking process. The reverse line movement guide explains why a line can move against public sentiment, while the closing line value guide covers price comparison after a market closes.
Calculator output is educational, not a prediction. UK-licensed operators must publish rules covering settlement, voids, errors, withdrawals and maximum payouts. Check the rules that apply to your bet and jurisdiction. See Gambling Commission LCCP 4.2.6.
Responsible use
Set a spending limit before gambling and do not chase losses. Read GambleAware's practical advice. Oddly Likely's responsible gambling page lists further support.
Once the calculation and risk checks are complete, you can compare betting partners. Oddly Likely may earn a commission from partner links; check the operator's current price, eligibility and terms. Read the affiliate disclosure.
Sources
- Gambling Commission, LCCP condition 4.2.6: Display of rules - betting. Current code accessed 30 July 2026.
- GambleAware, Advice to consider if you're gambling. Accessed 30 July 2026.