Decimal odds are the most widely used odds format in online sports betting globally. A decimal odds number represents your total return per unit staked, including the return of your original stake. This is the key distinction from fractional odds, which represent only the profit.
The calculation is simple: Total Return = Stake × Decimal Odds. A £20 bet at 3.50 returns £70 (£50 profit + £20 stake). A bet at 1.80 returns £18 on a £10 stake (£8 profit). Any decimal value above 1.0 is valid — below 2.0 is odds-on, exactly 2.0 is evens, above 2.0 is odds-against.
Comparing odds across bookmakers is trivial in decimal format. If Bookmaker A offers 2.30 and Bookmaker B offers 2.40 on the same outcome, the difference is immediately obvious. In fractional odds, comparing 5/4 against 11/8 requires mental calculation.
Accumulator calculations are cleaner in decimal. A four-fold with legs at 1.90, 2.10, 1.75, and 2.50 gives combined odds of 1.90 × 2.10 × 1.75 × 2.50 = 17.46. Just multiply all legs together. In fractional odds, each conversion step introduces opportunity for error.
Implied probability is the inverse of decimal odds. This makes decimal format especially useful for value analysis — you can instantly convert any price to a probability and compare it against your own estimates.
Example
You want to compare odds on Chelsea to win: Bookmaker A shows 7/4 (fractional), Bookmaker B shows 2.75 (decimal). Converting A to decimal: 7 ÷ 4 + 1 = 2.75. They are identical. Bookmaker C shows 2.80 — this is the best price, representing a 35.7% implied probability vs the 36.4% implied by 2.75.