The three formats
- Decimal (2.50) — bet 100, get 250 back (150 profit). Standard in Europe and on this site.
- Fractional (6/4) — profit to stake: bet 4, win 6. Traditional in the UK.
- American (+150 / −200) — plus: profit on a 100 stake; minus: stake needed for 100 profit. +150 = 2.50 decimal, −200 = 1.50 decimal.
Implied probability
For decimal odds: probability = 1 / odds. 2.50 → 40%, 1.50 → 66.7%. Real bookmaker probabilities sum to more than 100% — the excess is the margin.
Quick reference
2.00 = 1/1 = +100 = 50% · 2.50 = 6/4 = +150 = 40% · 1.50 = 1/2 = −200 = 66.7% · 3.00 = 2/1 = +200 = 33.3%. For any other value use the odds converter.