American odds, made clear.

Reading positive odds

At +150, a successful $100 bet earns $150 profit and returns $250 in total. You do not need to bet exactly $100: a $20 stake earns $30 profit and returns $50. The scale changes, but the ratio stays the same.

For positive American odds A, decimal odds = 1 + A ÷ 100. At +250, this is 3.50. The implied probability as a fraction is 100 ÷ (A + 100), or 2/7 here. Multiply that fraction by 100 to express it as a percentage: about 28.57%.

Reading negative odds

At −200, you would stake $200 to earn $100 profit. A $100 stake earns $50 profit and returns $150. At −110, $110 earns $100 profit, while $100 earns about $90.91.

For negative odds A, decimal odds = 1 + 100 ÷ |A|. The absolute value removes the negative sign. At −150, decimal odds are 1.666666…, and the break-even probability is 60%.

Even money and valid prices

Both +100 and −100 describe a 1-to-1 profit ratio, equivalent to decimal 2.00 or fractional 1/1. This calculator displays even money as +100.

Standard American odds use magnitudes of at least 100. Prices such as +50, −75 or 0 are not accepted. A plus sign can be omitted when entering a positive number.

A favourite is not a certainty

Negative odds usually price the more likely side of a two-way market, but the sign is a price convention, not proof about what will happen. Bookmaker margin, available information and market conditions all affect the listed price.

Compare the return for the same stake rather than comparing the absolute size of the American numbers. Decimal odds make that comparison particularly straightforward.

Explore the numbers

Use the calculators to try these examples with your own inputs. Calculations describe prices and conditional returns, not guaranteed outcomes.

Convert odds and calculate payout

Estimate fair odds from probability

Calculate expected value

Explore two-way sportsbook margin