Fractional vs. Decimal Odds: The Simple Conversion Guide

If you’ve grown up betting in the UK or Ireland, you’re probably used to fractional odds (e.g., 5/1, 9/4). But if you’re serious about value betting, or if you use exchanges like Betfair, you need to master decimal odds (e.g., 6.00, 3.25).

Decimal odds are the global standard for professional betting because they make calculating Expected Value (EV) and returns much easier.

On vibeodds you will see decimal prices wherever you work with data – especially in the [Value view](/value), where each runner’s decimal odds, fair odds and EV% are shown side by side.

This guide explains the difference, how to convert between them, and why vibeodds uses decimals for its calculations.

The Core Difference

Fractional Odds (e.g., 5/1)

  • Represent profit only.
  • They tell you: "For every 1 unit you stake, you will win 5 units of profit."
  • Total Return = Profit + Stake.

    • Decimal Odds (e.g., 6.00)

  • Represent total return (Profit + Stake).
  • They tell you: "For every 1 unit you stake, you will get back 6 units in total."
    • Example:
  • 5/1 means you win £5 for every £1 bet. Total return = £6.
  • 6.00 means your total return is £6 for every £1 bet.

    • They are exactly the same price, just expressed differently.

    How to Convert Fractional to Decimal

    The math is simple:
    Divide the fraction and add 1.

    Formula:

    (Numerator ÷ Denominator) + 1 = Decimal Odds

    Examples:

    1. 5/1
    * 5 ÷ 1 = 5
    * 5 + 1 = 6.00

    2. 9/4
    * 9 ÷ 4 = 2.25
    * 2.25 + 1 = 3.25

    3. 1/2 (Odds-on)
    * 1 ÷ 2 = 0.5
    * 0.5 + 1 = 1.50

    How to Convert Decimal to Fractional

    Subtract 1 from the decimal, then convert the remainder to a fraction.

    Formula:

    Decimal Odds - 1 = Fractional Profit

    Examples:

    1. 4.50
    * 4.50 - 1 = 3.50
    * 3.50 is 7/2

    2. 11.00
    * 11.00 - 1 = 10
    * 10 is 10/1

    Why Professional Bettors Use Decimals

    There are two main reasons why sharp bettors and platforms like vibeodds prefer decimal odds:

    1. Easier Probability Calculation

    To find the implied probability (the % chance the odds represent), you simply divide 1 by the decimal odds.
  • Odds of 4.00: 1 ÷ 4.00 = 0.25 (25%)
  • Odds of 2.00: 1 ÷ 2.00 = 0.50 (50%)

    • Trying to do this with fractions (e.g., 1 ÷ (3/1 + 1)) is clunky and prone to error.

    2. Essential for Expected Value (EV)

    Calculating EV requires comparing the true probability against the available odds. This math is seamless with decimals.
  • Formula: EV = (True Probability × Decimal Odds) × 100

    • If you want to learn more about how this works, check out our guide on What is Expected Value?.

    Summary Table

    | Fractional | Decimal | Implied Probability |
    | :--- | :--- | :--- |
    | 1/4 | 1.25 | 80.0% |
    | 1/2 | 1.50 | 66.7% |
    | Evens (1/1) | 2.00 | 50.0% |
    | 6/4 | 2.50 | 40.0% |
    | 2/1 | 3.00 | 33.3% |
    | 5/1 | 6.00 | 16.7% |
    | 10/1 | 11.00 | 9.1% |
    | 100/1 | 101.00 | 0.99% |

    Start Finding Value

    Now that you understand the odds, you’re ready to spot value. vibeodds does the hard work for you by scanning thousands of price points to find where the bookmakers have slipped up.

    Check out the [Live Odds page](/) to see real-time prices in decimal format, then switch to the [Value view](/value) to compare those odds to modelled fair prices and follow the outcomes through the [Results view](/results).

    Related Articles

  • What Is Expected Value?
  • How to Find Value Bets