Odds explained: decimal, fractional, American and implied probability

Odds are just prices with three dialects. This guide covers decimal, fractional and American odds, converting between them, what implied probability tells you, and the margin hidden inside every bookmaker price.

A betting education guide. No real money is involved anywhere on 1x2.social. 18+.

Decimal odds

Total returned per 1 unit staked, stake included — the format 1x2.social uses. Odds of 2.50 return 2.50u on a 1u stake (1.50u profit + 1u stake). Higher number, less likely, bigger payout. Simple to multiply, which is why accumulators quote in decimal.

Fractional odds

Profit relative to stake, traditional in the UK and Ireland: 3/2 means 3 units profit per 2 staked. Convert to decimal by dividing and adding 1: 3/2 = 1.5 + 1 = 2.50. Convert decimal back by subtracting 1: 2.50 − 1 = 1.50 = 3/2.

American odds

Plus = profit on a 100 stake (+150 → 150 profit on 100, decimal 2.50). Minus = stake needed to win 100 (−200 → stake 200 to win 100, decimal 1.50). Convert plus: (number ÷ 100) + 1. Convert minus: (100 ÷ number) + 1.

Implied probability and the margin

Implied probability = 1 ÷ decimal odds. Odds of 2.00 imply 50%; 1.25 implies 80% — also the win rate you need at those odds to break even. Bookmaker books always sum past 100% (the overround, ~105–110%): the margin is the bookmaker's cut, which is why our predictions strip it out before showing chances. Long-term profit means finding odds bigger than the true chance justifies — value — not picking winners. Short version in the glossary.