Fractional Odds Calculator — Betting Odds Converter
Enter fractional odds like 5/2 and your stake to instantly see the decimal odds, implied win probability, potential profit and total return — plus the equivalent American moneyline odds.
Stake returned plus profit if the bet wins
- 1
Profit ratio
5 ÷ 2 = 2.5Win this many units for every unit staked. - 2
Profit
10 × 2.5 = 25 - 3
Total return
10 + 25 = 35
How does this calculator work?
Fractional odds n/d mean you win n for every d staked. Decimal odds = n/d + 1; implied probability = d/(n+d); profit = stake × n/d. Enter any fractional odds and stake to see the payout, implied probability, and equivalent decimal and moneyline odds.
Formula
How this is calculated
Fractional odds, common in the UK and Ireland, express winnings relative to the stake. Odds of 5/2 ("five-to-two") mean you win £5 for every £2 you bet, plus your stake is returned — so a £2 bet that wins pays back £7 total. The numerator is the profit and the denominator is the stake unit.
Converting to decimal odds: decimal = (n/d) + 1. Decimal odds directly show the total return per unit staked, which makes it easy to compare across markets. The implied probability — the probability of winning the bet according to the bookmaker — is d/(n + d), or equivalently 1/decimal odds. In practice bookmakers build in a margin (overround), so implied probabilities across all outcomes sum to more than 100%.
American (moneyline) odds are derived from the decimal: if decimal ≥ 2, moneyline = +(decimal − 1) × 100; if decimal < 2, moneyline = −100 ÷ (decimal − 1). This calculator shows the equivalent for reference — no bookmaker margin is applied here.
Frequently asked questions
You win £5 for every £2 staked. So a £10 bet at 5/2 returns £35 total (£25 profit + £10 stake). Divide the numerator by the denominator to find the profit multiplier: 5÷2 = 2.5×.
Implied probability = denominator ÷ (numerator + denominator). For 5/2: 2 ÷ (5 + 2) = 2/7 ≈ 28.6%. The reciprocal of the decimal odds gives the same answer.
Bookmakers set odds so the implied probabilities across all outcomes add up to more than 100% — the excess is the overround (their built-in margin). This calculator shows the implied probability from a single outcome's odds; comparing the sum across all outcomes in a market reveals the bookmaker's edge.
Also known as
TG we-Calculate Editorial Team. (2026). Fractional Odds Calculator — Betting Odds Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/fractional-odds-calculator
TG we-Calculate Editorial Team. "Fractional Odds Calculator — Betting Odds Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/fractional-odds-calculator.
TG we-Calculate Editorial Team, "Fractional Odds Calculator — Betting Odds Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/fractional-odds-calculator
@misc{wecalculate_fractional_odds_calculator, title = {Fractional Odds Calculator — Betting Odds Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/fractional-odds-calculator}}, year = {2026}, note = {TG we-Calculate} }
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