Gambling terms, explained straight

Odds, Probability & Bankroll

Fractional odds to decimal

Converting fractional odds to decimal means dividing the numerator by the denominator and adding 1, so the decimal figure shows the total return per unit stake, including the original bet.

Conversion formula
Decimal odds = (a ÷ b) + 1 for fractional odds a/b12
Example: 4/1
(4 ÷ 1) + 1 = 5.0012
Example: 1/4
(1 ÷ 4) + 1 = 1.2512
General form
D = (a + b) ÷ b for odds a/b3

Key points

  • Fractional odds show profit only; decimal odds include the stake in the payout figure.12
  • To convert 2/1, divide 2 by 1 (= 2) then add 1 to get 3.00.
  • For odds like 6/4, divide 6 by 4 (= 1.5) then add 1 to get 2.50.
  • Even-money fractional odds 1/1 become 2.00 in decimal form.2
  • The conversion works for any fraction: the decimal odds represent the total payout per unit bet, not just the profit.3

Common fractional-to-decimal conversions

Quick reference for frequently seen odds.
Fractional odds Decimal odds
1/41.25
4/91.44
8/131.62
4/61.67
1/1 (evens)2.00
5/42.25
6/42.50
7/42.75
2/13.00
3/14.00
4/15.00
11/82.375
13/82.625
15/82.875

How to convert fractional odds to decimal

  1. Take the fractional odds, for example 6/4.
  2. Divide the numerator by the denominator: 6 ÷ 4 = 1.5.1
  3. Add 1 to include the stake: 1.5 + 1 = 2.50.12
  4. The result (2.50) is the decimal odds, meaning a £1 bet returns £2.50 total.

Why convert fractional odds to decimal?

Decimal odds are widely used in Europe, Australia and Canada because they make it easy to compare payouts across different bets. A single number tells you the total return per unit staked, including your original stake, so you can instantly see that 2.50 pays more than 2.00 without needing to interpret a fraction.1

Fractional odds, by contrast, show only the profit relative to the stake. Converting to decimal removes the mental arithmetic of dividing the fraction and adding the stake back, which is especially useful when comparing odds from different bookmakers or across different sports.2

The conversion is also essential for calculating implied probability. Decimal odds convert directly to probability via the formula 1 ÷ decimal odds, whereas fractional odds require an extra step: probability = denominator ÷ (numerator + denominator).3

Where this term is used

Not the same as

  • Decimal odds to American — a different conversion that turns decimal odds into American (moneyline) odds, not fractional into decimal
Odds & probability Fractional odds Explains the source format used in fractional-to-decimal conversion. Odds & probability Decimal odds to probability Shows how to turn decimal odds into implied probability percentages. Odds & probability Royal flush odds Covers the probability of being dealt a royal flush in poker. Odds & probability Risk vs odds Distinguishes between risk (probability) and betting odds. Odds & probability Odds vs probability Explains the difference between odds and probability in gambling. Odds & probability American odds Describes the moneyline odds format used in the US.

Sources

  1. Fixed-odds betting en.wikipedia.org Provides the conversion formula and examples for fixed-odds betting.
  2. Odds en.wikipedia.org Explains the relationship between fractional and decimal odds formats.
  3. Mathematics of bookmaking en.wikipedia.org Gives the general formula D = (a+b)/b for converting fractional odds.

Sources are drawn from regulators, universities and published research, and each one is labelled with what it actually is — a preprint is not called a paper. Bookmaker and affiliate pages are never cited here, because a page that sells betting is not a neutral authority on it.

Written and maintained by Ellis Warrender, writer and maintainer.

Last updated 28 July 2026. Spotted an error? Tell me and it gets fixed and logged on the corrections page.