Odds Converter Calculator
Convert between fractional, decimal and American odds, and see the implied probability each one represents — including the margin built into a set of prices.
The three formats describe the same thing differently.
How the odds converter calculator works
The three formats describe the same thing differently. Decimal odds are the total return per unit staked, so 3.00 returns three for one. Fractional odds are the profit against the stake, so 2/1 returns two profit plus the stake — the same as decimal 3.00. American odds show what a 100 stake wins (positive) or what must be staked to win 100 (negative).
Implied probability is simply 1 ÷ decimal odds. It is the useful number, because adding the implied probabilities of every outcome shows the bookmaker's margin: a fair two-way market sums to 100%, and anything above that is the overround, the built-in edge. This is arithmetic for reading a price, not advice about placing a bet.
Formula: decimal = fractional + 1; implied probability = 1 ÷ decimal
Worked examples
| Inputs | Implied probability | Note |
|---|---|---|
| Decimal 3.00 | 33.33% | 2/1, +200, 33.33% |
| Fractional 5/2 | 28.57% | decimal 3.50, 28.57% |
| American −150 | 60% | decimal 1.667, 60% |
| A two-way market summing to 105% | 50% | a 5% overround |
FAQFrequently asked questions
How do I convert decimal odds to fractional?
Subtract one. Decimal 3.00 is 2/1, decimal 1.50 is 1/2.
What is implied probability?
One divided by the decimal odds. A price of 4.00 implies a 25% chance.
What is the overround?
The amount by which every outcome's implied probability sums to more than 100%. That excess is the bookmaker's margin.
How do American odds work?
A positive number is the profit on a 100 stake; a negative number is what you must stake to win 100. +200 is decimal 3.00, −200 is decimal 1.50.
Does this predict anything?
No. It converts formats and shows what a price implies. It says nothing about whether the price is good value.
Where these figures come from
- World Handicap System — Rules of Handicapping — the score differential and handicap index formula
- International Cricket Council — Playing Conditions — over structure and run-rate definitions
- England and Wales Cricket Board — the national body for the sport these statistics most often describe here
Last checked: September 2026. Formulas follow the governing bodies where one publishes them — the World Handicap System for golf, the ICC playing conditions for cricket run rates.