Free Betting Tools
Sharpen your edge with these free calculators. No signup required.
Odds Converter
Convert between decimal, fractional, American odds and implied probability instantly.
Use tool →Arbitrage Calculator
Find sure bets and calculate optimal stakes for guaranteed profit across bookmakers.
Use tool →Margin Calculator
Calculate bookmaker margin, overround and fair odds for any betting market.
Use tool →Kelly Criterion Calculator
Find your optimal bet size using the Kelly Criterion. Includes fractional Kelly options.
Use tool →What these calculators do
These four tools cover the everyday maths of betting. The odds converter translates between decimal, fractional and American formats and shows the implied probability behind any price. The margin calculator reveals how much overround a bookmaker has built into a market, so you can see what fair odds would look like.
The other two are for bettors chasing an edge. The arbitrage calculator checks whether a set of odds across bookmakers adds up to a sure bet and splits your stake for a guaranteed return. The Kelly criterion calculator sizes bets based on your edge and bankroll, with fractional Kelly options for a more conservative approach.
They are useful for casual bettors comparing prices, value bettors sizing stakes, and developers sanity-checking their own calculations. If you want to automate any of this, the same numbers are available programmatically: our API covers odds from 265+ bookmakers across 34 sports, with a free tier of 100 requests per hour to get started.
See how we compare to other odds APIs: vs The Odds API · vs BetsAPI · vs OpticOdds