How do American and decimal odds relate?

For positive odds, decimal = 1 + odds/100. For negative odds, decimal = 1 + 100/|odds|.

Why is the fractional value approximate?

Fractional odds are rounded to a readable fraction, so the decimal equivalent can differ very slightly.

Whichever your sportsbook shows. Decimal is easiest for parlay math since you just multiply the legs.

Use the fair odds calculator to remove the estimated sportsbook margin from a price.

Type a price in any field — the other formats update automatically to match.

American

Decimal

Fractional

Implied probability (%)

American-110

Decimal1.909

Fractional10/11

Implied probability52.38%

Implied probability still contains the sportsbook's margin. It is the break-even win rate for that price, not an estimate of the true chance.

-110 is the same price as decimal 1.909, fractional 10/11, and an implied probability of 52.38%.

+250 is decimal 3.50, fractional 5/2, and 28.57% implied.

American: How much you win on a $100 stake (positive) or how much you must stake to win $100 (negative).
Decimal: Total return per $1 staked, including your stake back.
Fractional: Profit relative to stake, rounded to the nearest tidy fraction.
Implied probability: The break-even win rate for that price, with the sportsbook's margin still included.

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