Beginner's guide

How to Calculate Implied Probability from American Odds

Turn +150 or -120 into a percentage you can compare.

Written and reviewed by LineLens · Reviewed July 18, 2026 · 5–7 minute read

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The short answer

Implied probability converts a sportsbook price into the win rate needed to break even before removing vig. It puts positive and negative American odds on one percentage scale.

Simple example

For +150: 100 / (150 + 100) = 40%. For -120: 120 / (120 + 100) = 54.55%.

The formulas

For positive odds, use 100 / (odds + 100). For negative odds, use absolute odds / (absolute odds + 100). Multiply by 100 for a percentage.

What it means

A +150 price must win more than 40% of the time to profit over many identical bets. That is a break-even rate, not necessarily the true chance, because sportsbook prices include margin.

Use it carefully

  • Compare identical markets.
  • Remove vig before calling a probability fair.
  • Recheck the live price.
  • Remember that a probability never guarantees one result.

Keep learning

What Is No-Vig Probability?

Remove the sportsbook's built-in fee to estimate the market's fair probability.

What Does Positive EV Mean in Sports Betting?

Understand what a positive edge means—and what it does not promise.

What Is Closing-Line Value?

Compare your placed price with the market's last price before an event starts.