What are decimal odds?
Decimal odds are a single multiplier on your total return. A price of 1.91 means every dollar staked returns $1.91 when you win — your dollar back plus $0.91 of profit. Stake $100 at 1.91 and $191.00 comes back. There is no plus/minus sign convention to remember: bigger number, bigger payout, full stop.
The format dominates outside the US — European books, Australian books, and betting exchanges all deal in decimals — because it makes the two most important calculations trivial. Implied probability is just 1 ÷ the decimal price: 1.91 implies 52.4%. And parlays are multiplication: two legs at 1.91 each pay 1.91 × 1.91 = 3.65 combined.
Converting between decimal and American
For decimals of 2.00 or higher, subtract 1 and multiply by 100 to get a plus price: 2.50 becomes +150. For decimals below 2.00, divide −100 by the decimal minus 1: 1.91 becomes −100 ÷ 0.91 = −110. The crossover point is 2.00, which is exactly +100 — even money.
Notice that 2.00 also means a 50% implied probability. Above 2.00 you are on the underdog side; below it, the favorite side. Once you think in decimals, the probability content of any price is one division away — which is why exchange traders quote decimals even when discussing US markets: the price and the probability are the same number wearing two hats.
Why sharps prefer decimals
Serious staking lives on decimals because the math stays honest at scale. Expected value, parlay pricing, exchange trading, and devigging all reduce to multiplication and division on one number. Kelly sizing, hedge stakes, and cash-out comparisons collapse the same way — and every conversion you skip is one fewer place for an error to hide. This site renders American pills because that is the US board language — but every calculation underneath them runs in decimal and probability.
Worked example — 1.91, the world’s most common price
- Total return on $100
- $100.00 × 1.910 = $191.00
- Profit
- $191.00 − $100.00 = $91.00
- Implied probability
- 1 ÷ 1.910 = 52.4%
- To American (below 2.00)
- −100 ÷ (1.910 − 1) = −110
- Even money for reference
- 2.000 = +100 = 50.0%
1.91 is just −110 wearing a different uniform: 52.4% breakeven and $0.91 of profit per dollar. Convert fluently and no board on earth can hide its price from you.
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Frequently asked questions
How do I read decimal odds quickly?▾
Multiply your stake by the number — that is everything you get back, stake included. 1.91 on $100 returns $191.00. For profit, subtract your stake: $91.00. And for the implied chance, divide 1 by the price: 1 ÷ 1.91 = 52.4%.
What is 2.00 in decimal odds?▾
Even money — the same as +100 American. It returns double your stake and implies a 50% chance. Every price above 2.00 is an underdog; every price below it is a favorite.
Why do exchanges use decimal odds?▾
Because decimals are probabilities in disguise, and exchanges are probability markets. A 1.91 bid is a 52.4% opinion. Position sizing, hedging, and parlay math all stay as clean multiplication, with no sign conventions to fumble mid-trade.
Are fractional odds the same thing?▾
Fractional odds quote profit relative to stake — 10/11 is the same price as −110 and 1.91 — but they hide the total return and convert clumsily. Decimal folds the stake into the number, which is why it won out everywhere except US and UK retail boards.
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