Calculators built for sharp bettors.
Convert odds, size stakes with Kelly, model implied probability and build accumulators. Instant, accurate, no signup required. Educational tools only — never wager more than you can afford to lose.
Odds Converter
Decimal ↔ Fractional ↔ American with implied probability.
Update fractional or American manually
Kelly Calculator
Optimal stake sizing with Half / Quarter Kelly for real bankrolls.
Probability Calculator
Implied probability, bookmaker margin and no-vig fair odds.
A two-way market's total implied probability sits above 100% because the bookmaker prices in their margin. Strip the margin to see the fair line.
Accumulator Calculator
Combined odds and payout for 2–8 leg parlays.
Calculator FAQ
How do I convert decimal odds to American?+
For decimal odds of 2.00 or more, American = (decimal − 1) × 100. For decimal odds below 2.00, American = −100 / (decimal − 1). Our converter does this instantly for decimal, fractional and American formats.
What is the Kelly Criterion and how much of it should I use?+
Kelly Criterion is a stake-sizing formula f = (bp − q) / b, where p is your estimated win probability and b is the decimal odds minus 1. Most professionals use Half or Quarter Kelly to reduce bankroll variance.
How do I calculate the true probability implied by bookmaker odds?+
Implied probability = 1 / decimal odds × 100. To find the fair no-vig line in a two-way market, sum the implied probabilities and divide each odds by that total to strip the bookmaker margin.
How is an accumulator (parlay) return calculated?+
Multiply the decimal odds of every leg together, then multiply by the stake. Our accumulator calculator also shows the implied probability of every leg landing so you can see whether the payout is worth the risk.
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