Free tool
Convert American, decimal, and fractional odds — and see the implied probability behind any price. Instant, no signup.
-110 means risking $110 to win $100 — an implied probability of 52.4%. That extra 2.4% over a coin flip is the book's margin on a standard line. Enter any price and the converter shows the same three ways.
For negative American odds: decimal = 1 + 100/|odds|. For positive: decimal = 1 + odds/100. The converter handles both directions plus implied probability instantly.
No — it's the probability the PRICE implies, including the book's margin. Two-sided implied probabilities sum to more than 100%; the excess is the hold. Use the no-vig calculator to strip it out.
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The honest explainer
American, decimal, and fractional odds are the same fact in three dialects: how much a price pays relative to what you risk. Converting between them changes nothing about the bet — it just lets you compare prices without doing mental gymnastics.
The number that matters most is the implied probability: the win rate at which the price exactly breaks even. Every posted price is a claim about probability with the book's margin baked in — implied probability makes that claim visible.
A −150 favorite converts to decimal 1.67 and an implied probability of 60% (150 ÷ 250). Its +130 opponent converts to decimal 2.30 and 43.5% (100 ÷ 230). Add them: 103.5%. Real probabilities sum to 100% — the extra 3.5 points is the book's margin, split invisibly across both prices.