How do American odds work?

Q: How do American odds work?

American odds show a price relative to $100. A minus number (-150) is the amount you must risk to win $100. A plus number (+130) is the amount you win if you risk $100. Every price also implies a break-even win probability: minus odds are |odds| / (|odds| + 100), plus odds are 100 / (odds + 100).

Odds & Math

3 diagrams•5 min read•Updated Aug 22, 2026

Written by VIMB

Short answer

-150 means risk $150 to win $100. +130 means risk $100 to win $130. The bigger the minus number, the bigger the favorite.

American odds (also called moneyline odds) are the default format on US sportsbooks. They look confusing because they use two different rules depending on whether the number is negative or positive, but both rules are anchored to the same reference point: $100.

Reading a priceBoth formats are pinned to the same $100 reference.

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Minus odds = the favorite

A negative price tells you how much you have to risk to win $100. At -150, you risk $150 to win $100. If the bet wins you get back $250, your $150 stake plus $100 of profit. The further below zero the number goes, the heavier the favorite: -400 is a much bigger favorite than -120.

Plus odds = the underdog

A positive price tells you how much you win on a $100 risk. At +130, you risk $100 to win $130, and a winning ticket returns $230. The higher the number, the longer the shot.

Odds	Risk	To win	Total return
-250	$250	$100	$350
-150	$150	$100	$250
-110	$110	$100	$210
+130	$100	$130	$230
+300	$100	$300	$400

$100 is a unit of measure, not a bet size

Nothing forces you to bet $100. The odds scale proportionally. A $25 bet at +130 wins $32.50. The $100 is only there to make prices comparable.

Every price is also a probability

This is the part that turns odds from trivia into a tool. Any price can be converted into the win rate you would need just to break even on that bet. That number is the implied probability.

Minus odds: implied % = |odds| ÷ (|odds| + 100)

-150 → 150 ÷ 250 = 60.0%

Plus odds: implied % = 100 ÷ (odds + 100)

+130 → 100 ÷ 230 = 43.5%

So a -150 favorite has to win 60% of the time for that bet to be a wash, and a +130 underdog has to win 43.5% of the time. Your entire job as a bettor is finding spots where you believe the real chance is higher than the number the price demands.

What each price demandsThe break-even win rate hiding inside six common prices.

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Converting to decimal odds

Decimal odds (common outside the US, and on prediction markets and exchanges) express the total return per $1 risked, stake included. -150 is 1.67, +130 is 2.30. To convert: minus odds become 1 + (100 ÷ |odds|), plus odds become 1 + (odds ÷ 100).

The same price, four waysAmerican, decimal, fractional, and the break-even percentage behind each.

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Decimal is easier for math. Multiplying legs or comparing books is simple arithmetic in decimal, which is why most betting tools convert to it under the hood even when they display American odds.

Converting to fractional odds

Fractional odds, the standard in the UK, show your profit relative to your stake as a fraction: profit over stake. A minus price converts to 100 ÷ |odds|. -110 becomes 100/110, which reduces to 10/11. A plus price converts to odds ÷ 100. +300 becomes 300/100, which reduces to 3/1. Read the fraction as 'win this much for every this much you risk,' and it's the same number you already saw in the risk/to-win table above, just written as a ratio instead of two separate dollar amounts.

You don't need to memorize all of this

Every major sportsbook lets you set a default odds format in your account settings, American, decimal, or fractional. Pick the one that actually makes sense to you and the book will display every price that way from then on. The one number worth memorizing is the implied probability, since that's the only one that tells you whether a bet is actually worth making.