What is implied probability in sports betting?
Implied probability is the win rate a set of odds prices in — the percentage of the time a bet must win for you to break even at that price. It converts every odds format into one common currency, so a −110, a 1.91 decimal, and a 10/11 fractional all say the same thing: this side needs to win about 52.4% of the time.
The conversion depends on the sign. For negative odds, divide the price by the price plus 100: −110 becomes 110 ÷ 210 = 52.4%. For positive odds, divide 100 by the price plus 100: +150 becomes 100 ÷ 250 = 40.0%. The minus-side formula is the one you will use most, because most prop markets live between −130 and −130.
Why the two sides never sum to 100%
Add the implied probabilities of both sides of any market and you get more than 100% — typically 103% to 106% on player props. That excess is the bookmaker’s margin, the vig. A fair market would sum to exactly 100%; everything above it is the toll you pay to bet. Removing that excess to recover the true probabilities is called devigging, and it is the first move in any serious price comparison.
How to actually use it
Implied probability turns line shopping into arithmetic. If your estimate — from a model or a devigged sharp market — says a pitcher clears his strikeout line 55% of the time, any price implying less than 55% is a candidate bet. −110 at 52.4% qualifies; −130 at 56.5% does not. The entire +EV workflow is this comparison repeated across every book, every prop, every day.
It also keeps your expectations honest. At −110 you must win 52.4% of your bets just to break even. Win 50% — a coin flip — and you are slowly donating the vig.
Worked example — converting both signs
- Favorite: −110
- 110 ÷ (110 + 100) = 52.4%
- Underdog: +150
- 100 ÷ (150 + 100) = 40.0%
- Breakeven at −110
- win 52.4% of bets → $0.00 net
- Two-sided market: −110 / −110
- 52.4% + 52.4% = 104.8%
A two-way market summing to 104.8% is telling you the book took 4.8 points of margin off the top before you even picked a side.
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Related terms
Frequently asked questions
Is implied probability the same as the true probability?▾
No. Implied probability is what the price says; true probability is what actually happens. The two differ by the bookmaker’s margin and by whatever error the market has in its pricing. Beating the book means finding spots where your estimate of the true probability is higher than the implied one.
What is the implied probability of −110?▾
About 52.4%. The formula for negative odds is price ÷ (price + 100), so 110 ÷ 210 = 0.5238. That is why −110 is the sportsbook’s favorite default: both sides priced at 52.4% breakeven means the book collects margin from whichever side you take.
Why do implied probabilities add up to more than 100%?▾
Because sportsbooks are not charities. The amount over 100% is the overround — the margin baked into the market. A −110/−110 market sums to 104.8%; that 4.8-point excess is what the book expects to keep if action is balanced. Devigging divides it back out.
How does implied probability help me pick bets?▾
It gives you a breakeven line to compare against your own estimate. If you think a prop hits 55% of the time and the best available price implies 52.4%, you have an edge of 2.6 points. If no book is offering a price below your estimate, the correct bet is no bet.
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