Enter an odds value and select its format. The tool converts it to all other formats, shows implied probability, and optional profit if you add a stake.
Converted Odds & Implied Probability
Decimal Odds:
Fractional Odds:
American Odds:
Implied Probability:
Total Return:
Profit If Win:
Implied probability is the raw 1 / decimal odds figure. Because bookmakers add a margin, the implied probabilities of all outcomes in a market usually sum to more than 100% — your real edge depends on how your own estimate compares with the price.
Every odds format encodes the same two numbers: how much a winning bet pays and how likely the bookmaker rates the outcome. Converting between formats makes that probability explicit — the starting point for value betting and disciplined bankroll management.
How Conversion Works
All conversions pass through decimal odds. Fractional a/b becomes a/b + 1 (5/2 → 3.50); American +X becomes X/100 + 1 (+250 → 3.50) and -X becomes 100/X + 1 (-200 → 1.50). Implied probability is then 1 / decimal. Reading the formats: fractional quotes profit relative to stake, decimal quotes total return including stake, and American quotes profit per 100 staked (positive) or the stake needed to win 100 (negative).
Common Mistakes
Misreading the sign on American odds: +150 pays 150 profit on a 100 stake, while -150 requires a 150 stake to win 100 — confusing them misjudges the price by more than a factor of two.
Forgetting that fractional and American odds quote profit only, while decimal includes your stake — 3/1 equals decimal 4.00, not 3.00.
Treating implied probability as the true chance: margin inflates it, so summing a market's implied probabilities almost always gives more than 100%.
Worked Examples
Decimal to Fractional and American
A European bookmaker offers odds of 2.50 on a tennis match. Enter 2.50 in decimal format and the calculator converts it to 3/2 fractional (common in the UK) and +150 American (common in the US). The implied probability is 40%. With a £10 stake, your potential return is £25 (£15 profit). This makes it easy to compare the same odds across different regional formats.
American to Decimal Conversion
A US sportsbook lists a favourite at -200. Enter -200 in American format and the calculator shows this equals 1.50 in decimal and 1/2 fractional. The implied probability is 66.7%. For a $100 stake, your potential return is $150 ($50 profit). Negative American odds always represent favourites — the number shows how much you must stake to win $100.
Comparing Odds Across Bookmakers
Bookmaker A offers 6/4 fractional on a football match, while Bookmaker B lists the same selection at +140 American. Convert both: 6/4 = 2.50 decimal (implied probability 40%), while +140 = 2.40 decimal (implied probability 41.7%). Bookmaker A offers better value — 2.50 vs 2.40 decimal gives you an extra 10 cents per euro staked. Always convert to the same format before comparing.
They grew out of regional betting traditions: fractional odds come from British racecourses, decimal odds spread with European bookmakers and betting exchanges because they make return calculations trivial, and moneyline odds developed in US sports. All of them express the same underlying probability — only the notation differs.
No. Implied probability only tells you what the price assumes. To find an edge you need your own estimate of the true chance: if you rate a team 50% (fair odds 2.00) and the bookmaker offers 2.20 (45.5% implied), that 4.5-point gap is your theoretical edge. Without your own probability estimate, no price is inherently good or bad.
Every decimal price has an exact fractional equivalent, but it may be unwieldy (1.97 = 97/100), so bookmakers usually display the nearest conventional fraction. This converter shows the exact conversion; when a displayed fraction differs slightly from the decimal you compared, the price you are actually paid is the one on your bet slip.
