Road to Punter Series: What Is Implied Probability?

If you’ve placed more than a handful of sports bets, you’ve already met implied probability, even if you didn’t realize it at the time.

Bookmakers don’t pull odds out of thin air. Every number you see is backed by a percentage estimate of how likely an outcome is to happen. That percentage is the implied probability, and once you know how to read it, betting feels less like guessing and more like simple math actually working in your favor.

I’m Liz, and over at GoalBible, this is one of the first concepts I recommend learning. Not because it looks clever, but because it quietly decides whether you win over time or slowly hand money to the house while feeling optimistic.

Let’s break it down properly.

Implied Probability Meaning

Implied probability is the percentage chance of an outcome suggested by the odds set by bookmakers.

Before odds appear on any betting site, bookmakers estimate how likely each result is, including a win, loss, draw, or even player statistics and prop bets. This process is often called pricing or capping. They rely on data, match analysis, public betting behavior, and sometimes copying competitors.

Once those estimates are set, odds are created. Every odds type, whether fractional, decimal, or American, points back to a hidden percentage. That percentage is what truly matters.

Implied Probability Example

Let’s start with an easy one.

If a bet is priced at 3/1 (or 4.0 in decimal odds), the implied probability is 25%. That tells us the bookmaker believes this outcome should happen once in every four attempts.

Now here’s where things get interesting.

If you believe that the outcome should occur once every three attempts, or around 33%, then the odds are mispriced in your favor. That difference is what bettors call value, and value is the only reason to place a bet.

From my experience, chasing value beats chasing “sure wins” every single time.

Common Odds and Their Implied Probability

If you can glance at odds and roughly sense the percentage behind them, you’re already ahead of most bettors. Here’s a quick reference table for popular odds with their implied probability:

How to Calculate Implied Probability from Odds

Different regions prefer different odds formats, including Fractional, Decimal, and American/ Moneyline odds. For example, in an Arsenal vs Manchester United Premier League match, the odds clearly show how likely each result is based on bookmaker pricing. Let’s go through all three implied probability formulas.

Decimal Odds → Implied Probability

Decimal odds are the easiest and my personal favorite. They’re used widely across Europe and most global betting platforms.

Formula: Implied Probability = (1 ÷ Decimal Odds) × 100

Example: Arsenal to Win @ 1.40

1 ÷ 1.40 × 100 = 71.43%

That’s the bookmaker saying: “We strongly expect this team to win.”

Fractional Odds → Implied Probability

Fractional odds are still common in the UK. They show how much profit you make relative to your stake.

Formula: Denominator ÷ (Denominator + Numerator) × 100

Example: Arsenal vs Manchester United to Draw @ 4/1

1 ÷ (4 + 1) × 100 = 20%

Translation: bookmakers don’t fancy the draw much.

American (Moneyline) Odds → Implied Probability

American odds appear mostly in the US, Canada, and Mexico. They may seem confusing at first, but they’re predictable once you know the rules. There are two formulas, depending on the sign.

1. Positive American Odds (+)

Used for underdogs.

Formula: 100 ÷ (Odds + 100) × 100

Example: Manchester United to Win @ +650

100 ÷ (650 + 100) × 100 = 13.3%

In plain terms, bookmakers are pricing a Manchester United win as unlikely, giving it only a 13.3% chance.

2. Negative American Odds (–)

Used for favorites.

Formula: Odds ÷ (Odds + 100) × 100

Example: Arsenal to Win @ –238

238 ÷ (238 + 100) × 100 = 70.4%

Pretty close to what we saw using decimal odds earlier.

Implied Probability vs True Probability

Here’s the part bookmakers would rather you skip.

If you add up the implied probabilities of all possible outcomes in a match, the total usually exceeds 100%. That extra percentage is the bookmaker’s margin.

Using our earlier match example:

• Home win: 70.4%

• Draw: 20%

• Away win: 13.3%
  
  

Total: 103.7%

That extra 3.7% is how the bookmaker gets paid.

I actually like what I see from both 1Win and Roobet. The total implied probability sits only slightly above 100%, which tells me bookmaker margins are fairly low. From a bettor’s perspective, this is about as reasonable as pricing gets, and yes, that matters more than flashy promos.

Of course, this kind of pricing is not the norm. Plenty of bookmakers quietly shave down their odds below what they truly believe an outcome is worth. When that happens, the implied probabilities across all outcomes climb well past 100%, and that extra percentage is where the bookmaker makes their money. This is what people mean by the house edge or vigorish.

This is exactly why I always check implied probability first. It lets you see when the numbers are already stacked against you before you commit a single unit. Betting is hard enough without ignoring the math.

GoalBible Implied Probability Betting Strategy

This is the exact framework I stick to, and yes, it’s boring, which is why it works.

1. Estimate the probability yourself

Use stats, matchups, team news, historical data, or AI betting tools like ChatGPT to form your estimate. Keep it honest.

2. Convert the bookmaker’s odds into percentages

This takes seconds once you’re used to it.

3. Compare both numbers

If your estimate is higher than the bookmaker’s implied probability, you’ve found a value bet.

4. Repeat with discipline

Sticking to genuine value bets over time is how profits are actually made.

Final Verdict: Implied Probability Is Where Smart Betting Starts

Implied probability won’t make betting exciting. It won’t give you bragging rights. And it definitely won’t impress people who bet based on vibes.

What it will do is protect your bankroll and slowly tilt the odds back in your favor. And honestly, that’s the kind of edge I like. It keeps emotions out of the process and forces every bet to justify its price. Over time, that discipline matters far more than chasing the next big win story.

At GoalBible, I always say this: betting is less about picking winners and more about picking prices that don’t make sense.

FAQs

1. How do you calculate odds from implied probability?

To calculate odds from implied probability, use this formula: Odds = 1 / (1 - Implied probability)

For example, if the implied probability is 25%, the calculation looks like this:

Odds = 1 / 0.25 = 4.0

2. How do you calculate probability from fractional odds?

To find the percentage chance from fractional odds, use this formula: Percentage = [Denominator / (Denominator + Numerator)] x 100

For example, with odds of 3/1, the calculation would be: Percentage = 1 ÷ (1 + 3) x 100 = 25%

3. How do you convert odds into a percentage?

To convert odds into a percentage, use this formula: Percentage = [Denominator / (Denominator + Numerator)] x 100

For example, with odds of 2/1, the calculation is: Percentage = 1 ÷ (1 + 2) x 100 = 33.3%