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Odds Converter Calculator

Convert odds between Decimal, Fractional, and American formats and compute implied probability, profit, and total return for any stake.

Decimal ↔ Fractional American Odds Implied Probability Payouts

Odds Conversion & Payout Estimator

Enter odds in one format and get the equivalent odds, implied probability, and payout math. Build a table and export conversions to CSV.

Break-even: Implied probability is the break-even win rate for a bet at those odds (ignoring sportsbook margin). For decimal odds, break-even is 1/decimal. If you win more often than the implied probability, your long-run expectation becomes positive (again ignoring vig, limits, and price movement).
Sportsbook margin (vig): If you convert both sides of a market to implied probabilities, the total often exceeds 100%. That extra is the overround. To estimate “fair” probabilities you can normalize the implied probabilities so they sum to 100%.
Rounding: Converting between formats can introduce small differences due to rounding and fractional simplification. Use higher precision if you need closer matching across formats.

What Betting Odds Represent

Betting odds describe the relationship between risk and reward. They summarize how much you can win relative to your stake and also imply a break-even probability. Odds formats differ by region and market, but they all describe the same underlying quantity: the price of a wager.

An Odds Converter Calculator is useful when you see one format (like American odds for US markets, fractional odds in the UK, or decimal odds in many global sportsbooks and exchanges) but want to compare prices across platforms or compute implied probability quickly.

Decimal Odds Explained

Decimal odds show the total return per 1 unit staked, including your stake. If decimal odds are 2.50, a 1-unit stake returns 2.50 total, which equals 1.50 profit plus the 1-unit stake.

Decimal profit and return
Profit = Stake · (Decimal − 1)
Return = Stake · Decimal

Decimal odds are often the easiest format for comparing prices because the relationship to payouts is direct.

Fractional Odds Explained

Fractional odds show profit relative to stake. Fractional odds a/b mean you win a units profit for every b units staked. For example, 3/2 means 2 units stake yields 3 units profit, and total return is 5 units (profit + stake).

Fractional profit and return
Profit = Stake · (a/b)
Return = Stake · (1 + a/b)

Fractional odds are common in UK and Irish markets. They are often quoted in simplified fractions like 2/1, 5/2, 10/11, or 7/4.

American Odds Explained

American odds use a plus or minus sign. Positive odds (+A) tell you how much profit you win on a 100-unit stake. Negative odds (−A) tell you how much you must stake to win 100 units profit. This format is common in US sports betting.

American → Decimal
If +A: Decimal = 1 + (A/100)
If −A: Decimal = 1 + (100/A)

The converter uses the standard formulas to translate American odds into decimal odds and then into fractional odds and implied probability.

Implied Probability and Break-Even Rate

Implied probability is the chance of winning that makes your expected profit zero (ignoring sportsbook margin). It is often called the break-even probability. If your estimated true probability is higher than the implied probability, the bet may be positive value.

Implied probability
Decimal: p = 1 / Decimal
Fractional a/b: p = b / (a + b)
American +A: p = 100 / (A + 100)
American −A: p = A / (A + 100)

This calculator outputs implied probability for every conversion so you can compare prices and compute break-even quickly.

Profit vs. Total Return

Profit is your net winnings excluding the stake. Total return (also called payout) includes both the winnings and the original stake. Odds formats sometimes highlight profit (fractional) or return (decimal), so it helps to compute both from the same stake.

Why Conversions Can Differ Slightly

Odds conversions are exact mathematically, but sportsbook displays may show rounded values. Fractional odds are often simplified to a common denominator and American odds are usually quoted as whole numbers. When you convert and then convert back, the displayed results may shift slightly due to rounding.

If you need close matching, increase decimal precision and choose “Keep exact” for fractional conversion. If you prefer standard bookmaker-style fractions, choose a max denominator such as 10 or 20.

Odds Tables for Quick Reference

The Conversion Table mode builds a set of conversions across a range of decimal odds. This is useful for:

  • Building personal cheat sheets
  • Comparing exchange prices vs sportsbook prices
  • Teaching or documenting odds formats
  • Quickly estimating implied probability at common prices

You can also export the table to CSV for spreadsheets or analysis.

FAQ

Odds Converter Calculator – Frequently Asked Questions

Answers about odds formats, implied probability, payouts, and conversion rounding.

An odds converter changes betting odds between formats such as decimal, fractional, and American. It also helps calculate implied probability and expected payouts from a stake.

Decimal odds show the total return (including stake) per 1 unit staked. For example, 2.50 means a 1-unit stake returns 2.50 total, for 1.50 profit.

Fractional odds show profit relative to stake. For example, 3/2 means you win 3 units profit for every 2 units staked (plus your stake back).

American odds use + or −. Positive odds (e.g., +150) show profit on a 100-unit stake. Negative odds (e.g., −200) show how much you must stake to win 100 units profit.

Implied probability is the break-even chance. For decimal odds it is 1/decimal. For American odds: +A implies 100/(A+100), and −A implies A/(A+100).

Profit is winnings excluding the original stake. Total payout (return) includes the stake plus profit.

Sportsbooks include a margin (vig/overround). Converting each side to implied probability typically totals more than 100% unless you remove the margin.

Yes. Enter a stake amount and the calculator shows profit and total return for each odds format.

Rounding can slightly change implied probability and payout figures. Use higher precision if you need closer matching across formats.

Yes. Build a conversion table and export it to CSV for recordkeeping or spreadsheet analysis.

This tool is for informational use. Odds, margins, rules, and payouts vary by bookmaker and market. Always confirm final pricing and settlement rules before betting.

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