Betting Odds Converter

Add the implied probabilities and the margin appears.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Odds given as

Odds

For fractional, this is the numerator

Stake

Odds

3 decimal

2/1 · +200 · implies 33.33%

Decimal3

Fractional2/1

Moneyline+200

Implied probability33.333%

Break-even win rate33.333%

Profit if it wins20.00

Total return30.00

Implied probability is 1 divided by the decimal odds, and it is the number that makes bets comparable across formats. It is also how a bookmaker's margin becomes visible: add the implied probabilities of every outcome in a market and the total exceeds 100%, and the excess is the margin. A two-way market quoted at 1.91 on both sides sums to 104.7%, so the book is taking 4.5% whatever happens. You need to beat 33.3% to break even on this bet.

How the Betting Odds Converter works

Odds converted between decimal, fractional and moneyline, with implied probability and the break-even win rate. Implied probability is what makes bets comparable, and adding it across a market reveals the bookmaker's margin.

Also known as: decimal to fractional odds converter · moneyline to decimal odds · implied probability from odds · what do 5/1 odds mean

Three formats, one bet

Decimal odds give the total return per unit staked, including the stake. Fractional odds give profit relative to stake. Moneyline gives profit on 100 staked, or the stake needed to win 100.

Odds of 3.0, 2/1 and +200 are the same bet. The formats are regional conventions (fractional in Britain and Ireland, moneyline in North America, decimal nearly everywhere else) and they are frequently quoted without being labelled.

Implied probability is 1 divided by the decimal odds, and it is the number that makes bets comparable across formats. It is also the win rate you must beat to break even, which is the only figure that decides whether a bet is worth taking.

The overround makes the margin visible

Add the implied probabilities of every outcome in a market. If the total exceeds 100%, the excess is the bookmaker's margin — and it always exceeds 100%.

A two-way market quoted at 1.91 on both sides implies 52.4% each, summing to 104.7%. The book collects 4.5% regardless of which side wins, which is where the profit comes from.

This is why odds move: to balance the book against money taken, so the margin is collected whatever happens. A bookmaker aims to profit from the spread rather than from predicting outcomes, which is a different business from betting.

What value actually means

A bet has value when your estimate of the true probability exceeds the implied probability. That is the only circumstance in which it has positive expected value, and it requires your estimate to be better than the market's.

Closing line value — whether the odds you took were better than the final price — is the most reliable indicator of whether a bettor is genuinely beating the market rather than getting lucky over a short run.

Staking systems cannot manufacture value. Doubling after a loss redistributes variance and leaves expected value unchanged, because the house margin applies to every bet regardless of how the stakes are sized.

Where to go next

The Betting Odds Converter question rarely arrives on its own. These are the ones that usually come with it:

Parlay Calculator — The margin compounds along with the odds.
Lottery Odds Calculator — Weekly play would take longer than recorded history.
Dice Probability Calculator — Seven has six ways; twelve has one.
Percentage Calculator — Every common percentage question in one place.

Frequently asked questions

How do I convert decimal odds to probability?

Divide 1 by the decimal odds. Odds of 4.0 imply a 25% chance, and that figure is the win rate you must beat to break even.

What do fractional odds mean?

Profit relative to stake. Odds of 5/1 return five in profit plus your stake, which is decimal 6.0. Odds of 1/5 return one profit for five staked, which is decimal 1.2.

How does moneyline work?

A positive number is the profit on a 100 stake; a negative number is the stake needed to win 100. +200 is decimal 3.0 and −150 is decimal 1.667.

What is the overround?

The amount by which implied probabilities across a market exceed 100%. A two-way market at 1.91 each side sums to 104.7%, so the bookmaker takes 4.5% regardless of the result.

Why do odds move?

To balance the book against money taken, and to reflect new information. A bookmaker aims to profit from the margin rather than from predicting outcomes, which is why heavy backing shortens a price.

What is value in betting?

When your estimate of the true probability exceeds the implied probability. It is the only circumstance in which a bet has positive expected value, and it requires your estimate to be genuinely better than the market's.

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