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Implied Probability Explained

Implied probability is the percentage chance a set of odds is quietly telling you. Decimal odds of 2.00 imply a 50% chance. Odds of 1.50 imply about 66.7%. The formula is one division: implied probability = 1 ÷ decimal odds, then multiply by 100.

That single number is the most useful thing you can pull from a price. It lets you compare a bookmaker's opinion against your own read on a game, and it exposes the margin baked into every market. This guide walks through the maths in decimal (the format most sportsbooks in Ontario default to), shows you a full worked example on an NHL moneyline, and explains why the implied probabilities on any market always add up to more than 100%.

The formula: from decimal odds to a percentage

For decimal odds the conversion is:

implied probability (%) = (1 ÷ decimal odds) × 100

A few reference points you'll see all over the schedule:

Shorter odds mean a higher implied probability (the favourite). Longer odds mean a lower implied probability (the underdog). The number is not a guarantee — it's the price dressed up as a percentage, and that price already includes the operator's cut.

If your book shows American odds, the maths splits in two. For a negative line like -150: probability = 150 ÷ (150 + 100) = 60.0%. For a positive line like +200: probability = 100 ÷ (200 + 100) = 33.3%. You can always convert American to decimal first, then use the single decimal formula if you prefer to stick to one method.

Worked example: an NHL moneyline

Say two Ontario-licensed sportsbooks are pricing an NHL game. Book A has the home side at 1.80 and the visitors at 2.10. Convert both:

Add them: 55.6% + 47.6% = 103.2%.

A fair two-way market should total 100%. This one totals 103.2%, so the extra 3.2 percentage points is the bookmaker margin (also called the overround or vig). That margin is how the book makes money regardless of who wins.

To strip it out and see the 'true' implied probabilities, divide each by the total:

These now add to 100%. So the book's genuine opinion is closer to 53.9% for the home team, and the 55.6% figure was inflated by the margin. If your own model says the home side should win 58% of the time, the price at 1.80 is offering you value — you rate them higher than the market does after margin is removed.

Implied Probability Calculator

152.6% (fair 50.5%)
X27.8% (fair 26.7%)
223.8% (fair 22.8%)
Margin4.22%

Why every market adds up to more than 100%

On a fair coin, heads and tails each imply 50% and total exactly 100%. Sportsbook markets never do that. The sum always exceeds 100%, and the surplus is the margin.

The tighter that surplus, the better the price for you. In our sampled odds data the margin gap between operators is real and measurable:

A 3% margin versus a 6.9% margin is the difference between the book skimming three cents or nearly seven cents off every fair dollar. Over a season that gap decides whether a bettor breaks even. This is why comparing prices before you place a bet matters more than any single headline odds figure. You can line the same fixture up across books on our betting odds Canada pages.

Best-price share: who actually posts the sharpest number

Margin tells you the average tightness of a market. Best-price share tells you how often a given book actually has the top number on a fixture when you line everyone up side by side.

From the same sample:

The two are related but not identical. Pinnacle carries the lowest margin yet DraftKings edges it on how often it holds the single best price across the wider sample. For implied probability that means: convert the odds, then check who's giving you the highest decimal (lowest implied probability against your pick) before you commit. A market mover on one book is often a stale price on another — track those shifts on our market movers feed.

Using implied probability to find value

Value exists when your estimated probability is higher than the price's implied probability after margin. The rule of thumb:

Work it in the order that keeps you honest:

1. Set your own probability for the outcome before you look at the price. 2. Convert the book's odds to implied probability with 1 ÷ decimal. 3. Strip the margin by dividing by the market total (as in the NHL example). 4. Compare. Only bet when your number clears the book's true number by a margin you're comfortable with.

Doing step one first stops you from anchoring to the price. This is the discipline behind every worthwhile call on our predictions pages — the number has to beat the market's implied read, not just feel right. It applies the same way to an NFL spread, an NBA total, a UFC / MMA moneyline or a Champions League outright.

Where the format shows up in Ontario

Most sportsbooks registered with iGaming Ontario let you switch odds display between decimal and American. Decimal makes implied probability trivial — one division and you're done — which is why the examples here use it.

Every operator listed on BETARVO for Canada runs at a C$10 minimum deposit, supports Interac and settles withdrawals in a 0–24h window, so the practical friction of moving between books to price-shop is low. The regulatory picture is provincial, though: AGCO and iGaming Ontario license online betting in Ontario specifically, not across Canada. Other provinces run their own regimes through provincial lottery corporations and regulators, so which books you can legally use depends on where you live. The legal minimum age is 19.

For picking where to price-shop, start with the best betting sites Canada shortlist, then narrow by sport — NHL bettors can jump straight to Ice Hockey betting sites and NFL bettors to American Football betting sites.

FAQ

What is implied probability in betting?

It's the percentage chance a set of odds represents. For decimal odds you calculate it as 1 ÷ decimal odds × 100. Odds of 2.00 imply 50%, and 1.50 imply 66.7%. It reflects the bookmaker's price, including their margin — not a guaranteed outcome.

How do I convert decimal odds to a percentage?

Divide 1 by the decimal odds and multiply by 100. For example, 2.50 becomes 1 ÷ 2.50 = 0.40 → 40%. Longer odds give a lower percentage; shorter odds give a higher one.

Why do implied probabilities add up to more than 100%?

The surplus above 100% is the bookmaker margin — the vig or overround. In our NHL example the two sides totalled 103.2%, so 3.2 percentage points was margin. Dividing each side's implied probability by that total strips the margin out and returns figures that add to 100%.

How do I remove the margin to find the true probability?

Add the implied probabilities of every outcome in a market, then divide each individual outcome by that total. If home implies 55.6% and away 47.6% (total 103.2%), the true figures are 53.9% and 46.1%, which now sum to 100%.

How does implied probability help me find value?

Estimate the outcome's probability yourself before checking the price. Convert the odds to implied probability, strip the margin, then compare. If your figure is higher than the book's true implied figure, the price may hold value. If it's lower, the price is too short.

Which sportsbook gives the tightest margins in the sample?

In our sampled odds data Pinnacle carried the lowest average margin at 3.12%, followed by FanDuel at 4.06% and DraftKings at 4.21%. On best-price share — how often a book posts the single top number — DraftKings led at 54.5%, just ahead of Pinnacle at 53.4%.