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.
Remove vig from a market
Measure the book percentage, overround and normalised no-vig probabilities for two to six outcomes.
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.
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.
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.