What is implied probability?

Implied probability is the likelihood of an outcome expressed as a percentage, derived directly from the odds. For example, decimal odds of 2.00 imply a 50% chance of winning. Bookmakers build a margin (overround) into their odds, so the sum of implied probabilities across all outcomes typically exceeds 100%.

How do I convert fractional odds to probability?

For fractional odds expressed as A/B, the implied probability is B / (A + B). For example, 3/1 odds give 1 / (3 + 1) = 0.25, or 25%.

How do American moneyline odds work?

Positive odds (e.g. +200) show profit on a $100 bet. Negative odds (e.g. -150) show how much you must bet to win $100. Positive: probability = 100 / (odds + 100). Negative: probability = |odds| / (|odds| + 100).

What is the difference between decimal and fractional odds?

Decimal odds include the return of your stake. Fractional odds represent only the profit relative to the stake. Decimal odds = (fractional numerator / denominator) + 1. So 3/1 fractional = 4.00 decimal.

Can I use this for non-betting probability conversions?

Yes. Odds are used in statistics, epidemiology, and game theory. This tool converts between any odds representation and probability, regardless of the context.

Odds to Probability Converter

Name: Odds to Probability Converter
Availability: InStock
Author: Nham Vu

Enter odds in any format — fractional, decimal, or American — and instantly see the implied probability and all equivalent odds formats.

Enter Odds

Odds Format

Fractional Odds (e.g. 5/2)

Numerator / Denominator — profit per stake unit

Enter odds on the left and press Convert

Implied Probability

— %

0% 50% 100%

All Formats

Fractional

—

Decimal

—

American (Moneyline)

—

Common Odds Reference

Fractional	Decimal	American	Probability

Copied!

Summary

Enter odds in any format — fractional, decimal, or American — and instantly see the implied probability and all equivalent odds formats.

How it works

Select the odds format you want to enter: fractional (e.g. 5/2), decimal (e.g. 3.50), or American (e.g. +250 or -150).
Type the odds value into the input field.
The tool instantly calculates the implied probability percentage.
All three equivalent odds formats are displayed together so you can compare them.
Use the copy buttons to grab any value for use elsewhere.

Use cases

Understand the implied win probability behind a sportsbook line.
Cross-check odds across bookmakers that display different formats.
Convert American moneyline odds to decimal for use in expected value formulas.
Compare fractional odds between horse racing and soccer markets.
Calculate breakeven win rate needed to profit from a bet.
Teach students the relationship between probability and odds formats.
Verify odds calculations in custom betting spreadsheets.
Quickly convert odds when reading international sports coverage.

Frequently Asked Questions

Related tools

Complement Probability Calculator Probability Intersection Calculator

Last updated: 2026-05-23 · Reviewed by Nham Vu