Guides / Implied probability

Implied probability and the vig

Every price carries a probability. Once you can read it, you can see how much of a price is the sportsbook's margin and how much is its view of the game.

From odds to probability

Minus odds: probability = |odds| / (|odds| + 100). At -150: 150 / 250 = 60.0%.
Plus odds: probability = 100 / (odds + 100). At +150: 100 / 250 = 40.0%.

Why a two-way market adds up to more than 100%

A standard spread is -110 on both sides. Each side implies 110 / 210 = 52.38%. The two together are 104.76%, not 100%. The extra 4.76% is the sportsbook's margin, the vig.

Side	Odds	Implied probability
Team A	-110	52.38%
Team B	-110	52.38%
Total		104.76%

Removing the vig (no-vig or fair odds)

The simplest method is proportional: divide each side's implied probability by the total. For two -110 sides that gives 52.38 / 104.76 = 50.0% each, so the fair price is +100 on both. For lopsided markets there are other methods, and they give slightly different answers, so treat a no-vig price as an estimate.

An uneven example

Team A is -150 (60.0%) and Team B is +130 (43.48%). The total is 103.48%. Dividing each by 1.0348 gives about 57.98% and 42.02%. So the market's "fair" view is roughly 58 / 42, while the displayed prices overstate both sides.

Why it matters: to profit over time you have to beat both the market's opinion and the vig. Knowing the vig on a price tells you how much better than 50/50 your own estimate has to be just to break even (52.38% at -110). This is information, not advice, and results are never guaranteed.

Use the odds converter to check any price.