The US betting format: positive odds show profit on a £100 stake; negative odds show the stake required to profit £100.
American odds are expressed relative to a £100 (or $100) benchmark. Positive odds (e.g. +250) show your profit on a £100 stake — bet £100 to win £250 profit (£350 total return). Negative odds (e.g. -150) show how much you must stake to profit £100 — stake £150 to win £100 profit (£250 total return).
Positive American odds indicate underdogs (implied probability below 50%); negative American odds indicate favourites (implied probability above 50%). Evens in American is +100.
Positive to decimal: (American ÷ 100) + 1. +250 → 2.50 + 1 = 3.50. Negative to decimal: (100 ÷ |American|) + 1. -150 → (100÷150) + 1 = 0.667 + 1 = 1.667. Implied probability for positive: 100 ÷ (odds + 100). For negative: |odds| ÷ (|odds| + 100). -150: 150 ÷ 250 = 60%.
Decimal Odds
The standard odds format in Europe and on exchanges, expressing total return per unit staked — including the return of the stake itself.
Fractional Odds
The traditional UK odds format, expressing profit relative to stake as a fraction — 3/1 means £3 profit for every £1 staked.
Implied Probability
The probability of an outcome embedded in bookmaker odds — calculated by dividing 1 by the decimal odds.
For informational and educational purposes only. Disclaimer
