Betting calculators and tools
Betting maths isn’t hard, but it’s easy to get wrong in your head at the moment you’re about to press “place bet”. These betting calculators do the arithmetic so you can spend your attention on the only question that matters: is this price any good?
I keep them simple on purpose. Each tool does one job, shows its formula, and works on your phone. They run in your browser. Nothing you type is saved, there’s no account, and no bookmaker is waiting at the end with an offer.
Two are live now. The parlay calculator multiplies your legs, shows the payout and then shows the number the bet slip leaves out: how often a bet like that actually wins. The odds converter translates between decimal, fractional and American odds and tells you the implied probability of any price, with a full conversion table underneath.
One warning. A calculator tells you what a bet pays. It can’t tell you whether the bet is smart, and no tool on any site can. Use these to check the numbers, then decide with a clear head. Bet only what you can afford to lose. 18+.
Calculators you can use now
Free parlay calculator: type each leg's odds and your stake to see combined odds, payout, profit and the chance the whole bet actually wins.
Open the parlay calculatorFree odds converter: type decimal, fractional or American odds, or a probability, and get the other three at once. Conversion table included.
Open the odds converter
Coming later
Planned, not built yet. No dates, because I would rather ship them right than ship them fast.
- Implied probability calculatorSoonTurn a whole market into percentages and see the bookmaker margin.
- Kelly criterion calculatorSoonHow much to stake when you think you have an edge, and why half of that is usually wiser.
- Each-way calculatorSoonWin and place returns for horse racing and golf bets.
- Hedging calculatorSoonWhat to stake on the other side to lock in a return or cut a loss.
Read before you calculate
A calculator is only as good as the numbers you feed it. Start with these.
How Do Betting Odds Work? Decimal, Fractional and American Odds Explained
How do betting odds work? Decimal, fractional and American odds explained with worked payouts, implied probability and the bookmaker's hidden margin.
What Is a Parlay? Accumulators and Multis Explained With Real Maths
What is a parlay? How accumulators and multis pay, the maths behind the odds, why bookmakers love them and what changes with same-game parlays.
Betting Bankroll Management: Units, Staking Plans and Surviving Bad Runs
Betting bankroll management in plain English: set a bankroll, size a unit, pick flat or percentage staking, use Kelly safely and survive losing runs.
Terms the calculators use
Betting calculators: questions
Are these betting calculators free?
Yes, all of them, with no account and no sign-up. They run in your browser, so nothing you type is stored or sent anywhere.
Can a calculator tell me if a bet is good?
No. It tells you what a bet pays and what chance the odds imply. Whether the real chance is higher than that is your call, and it's the only thing that decides if a bet has value.
Which odds formats do the tools support?
Decimal, fractional and American in both tools. The odds converter also takes an implied probability, so you can go from a percentage back to a price.