How do I convert American odds to decimal?

For a positive price, decimal = 1 + (odds ÷ 100), so +150 becomes 2.50. For a negative price, decimal = 1 + (100 ÷ |odds|), so −200 becomes 1.50.

How do I convert fractional odds to decimal?

Divide the numerator by the denominator and add 1. 5/2 becomes 1 + 2.5 = 3.50, and evens (1/1) becomes 2.00.

Which format is best?

Decimal is easiest for maths because it is a direct multiplier. American is standard in the US, fractional in UK and Irish horse racing. They express the same price.

Why do converted fractional odds look unusual?

Fractional odds are reduced to their simplest whole-number ratio, so a decimal price of 1.91 shows as roughly 10/11 rather than an exact match. Decimal keeps the full precision.

Odds Converter

Decimal, American and fractional odds are three ways of writing the same number. Enter a price in any format to see the other two, plus the probability it implies.

Input format

Odds to convert

Decimal

2.50

American

+150

Fractional

3/2

Implied probability

40.00%

1 in 2.5

The formulas

Conversions, using decimal as the pivot

American (+) → decimal = 1 + odds ÷ 100

American (−) → decimal = 1 + 100 ÷ |odds|

Fractional a/b → decimal = 1 + a ÷ b

decimal → American (≥2.00) = (decimal − 1) × 100

decimal → American (<2.00) = −100 ÷ (decimal − 1)

decimal → probability = 1 ÷ decimal × 100

Every calculator on bet.ing converts your input to decimal first, so results stay consistent whatever notation you prefer.

Conversion table

Common prices in all three notations with implied probability.
Decimal	American	Fractional	Implied probability
1.20	−500	1/5	83.33%
1.50	−200	1/2	66.67%
1.75	−133	3/4	57.14%
1.91	−110	10/11	52.36%
2.00	+100	1/1	50.00%
2.50	+150	3/2	40.00%
3.00	+200	2/1	33.33%
5.00	+400	4/1	20.00%
11.00	+1000	10/1	9.09%
26.00	+2500	25/1	3.85%

Common mistakes

Forgetting the +1 in decimal odds. Decimal includes your stake; fractional and American describe profit only.
Treating −110 and 110 as the same price. −110 is a short price (52.36%); +110 is a longer one (47.62%).
Comparing prices across books in different formats. Convert both to decimal before deciding which is better.

Frequently asked questions

Last reviewed: 24 August 2026. Formulas on this page are checked against the unit test suite that powers every bet.ing calculator.