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How to Convert Odds

28th February 2019 / Julian
Betting Advice

Betting odds are all about chance and probability. Commonly displayed as either fractions or decimals, odds are the marker for bookmakers prices. You may also come across American (also known as Moneyline) odds, especially if you’re being adventurous in your markets, or travelling.

These are displayed as positive figures where the odds state the winnings on a £100 bet, or negative figures, where the odds state how much must be bet to win a £100 profit.

Whether you need to convert betting odds to percentages, fraction to odds, or to convert percentage to odds, the process will play a crucial part in your decisions of what to bet on and how much to wager. Knowing how to convert odds from one format to another is very useful, so we’re going to tell you just how to do it.

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But why do I need to do it?

No doubt you’re asking this question and wondering, “Why is this important in the first place?” It’s all about understanding the implied probability – which is depicted in the form of a numeric percentage – behind the odds on offer, so that you can then analyse it and ascertain the value in any given bet. The bookmaker won’t provide a full rundown of all this information, so it’s up to you to accrue and deconstruct it.

If the implied probability on a wager is less than your own estimated probability of a particular outcome, then that bet represents a what’s known as a value betting opportunity. In other words, a great deal. So now you know that you’re likely to make some moolah by doing this, read on to find out exactly what it is you need to do.

So how do I do convert odds?

There are two ways you can go about this. Either search online for a betting odds calculator which will do the work for you. Or become your own betting odds converter. If you choose the latter, here are the questions and the formulas you’ll need to look at:

  • What is the odds format you want to convert?
  • What format do you want to convert them too?
  • What is the implied probability of the odds you’re starting with?

To find the answer to the third question, use the appropriate one of the following formulas:

  • For fractional odds the denominator / (denominator + numerator*) = Implied probability
  • For decimal odds 1 / “Decimal Odds” = Implied probability
  • For American odds ( – ( ‘minus’ American odds ) ) / ( – ( ‘minus’ moneyline odds ) ) + 100 = Implied probability

* the numerator is the number to the left of the slash, with the denominator to the right.

Once you’ve mastered these calculations, converting implied probability is straightforward, here are the formulas you’ll need:

  • ( 100 / implied probability ) -1 = fractional odds
  • 100 / implied probability = decimal odds
  • ( implied probability / (100 – implied probability)) x 100 = American odds (this formula applies to implied probability of 50% and above only)
  • (100 – implied probability / implied probability ) x 100 = American odds (this formula applies to implied probability of 50% and below only)

Further formulas

Once you have the implied probability, you can then use the above equations to transfer it on into whatever odds type you wish. However, if you want to convert different formats directly into decimal odds (or vice versa), these are the formulas to use:

  • For fractions into decimals: (numerator/denominator) + 1 = decimal odds
  • For positive American odds into decimals: (American odds / 100) + 1 = decimal odds
  • For negative American odds into decimals: (100 / American odds) + 1 = Decimal odds
  • For fractions into positive American odds: (Moneyline/100) = fraction
  • For fractions into positive American odds: (100/Moneyline) + 1 = fraction

A better understanding of odds

If this all seems a bit overwhelming, don’t be deterred. It’s perhaps a little advanced for those who are relatively inexperienced, and help is at hand. There are plenty of betting calculator odds tools on the web that will help you convert odds to their implied probabilities and convert odds to other formats.

So you may be wondering why it’s worth all the bother of doing it the manual way, when a machine can do it for you?

The payoff

It is a little time consuming and a hassle to be bothering with equations. Nevertheless, it’s a thoroughly worthwhile exercise. Understanding the calculations behind these conversions, particularly if you want to be, or are, a professional bettor is a very useful level of insight in analysing the market.

The process will help you better understand what the odds represent in terms of value, instinctively. Where there is little time, or a snap decision is required, your brain will jump to the correct conclusions automatically, making you money in the process, as well as encouraging you to analyse the implied probabilities when you see the odds on offer.

The tip is based on the personal opinion of the author. No success is guaranteed. Please gamble responsibly. 18+

* All mentioned odds were valid at the time of writing. Betting odds are subject to fluctuations. Please check the current odds with the respective bookmaker!

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