What does +150 mean in American odds?

A +150 price means a $100 bet wins $150 in profit if the bet wins (returning $250 total: your $100 stake + $150 profit). The + indicates an underdog: the team or outcome is less likely than 50/50 to win, so the sportsbook pays more than even money to attract action.

What does -180 mean in American odds?

A -180 price means you must risk $180 to win $100 in profit. The - indicates a favorite: the team or outcome is more likely than 50/50 to win, so the sportsbook pays less than even money. A successful $180 bet at -180 returns $280 total ($180 stake + $100 profit).

How do I convert American odds to implied probability?

For positive odds (+150): probability = 100 / (odds + 100) = 100/250 = 40%. For negative odds (-180): probability = odds / (odds + 100) = 180/280 = 64.3%. Implied probability includes the operator margin (vig), so it overstates true probability by 4-7 percentage points typically.

How do I convert American odds to decimal odds?

For positive odds (+150): decimal = (odds / 100) + 1 = 2.50. For negative odds (-180): decimal = (100 / odds) + 1 = 1.556. Decimal odds are the European standard and represent total return including stake (a $100 bet at decimal 2.50 returns $250 total).

How do I convert American odds to fractional odds?

For positive odds (+150): fractional = odds/100 = 150/100 = 3/2. For negative odds (-180): fractional = 100/odds = 100/180 = 5/9. Fractional odds are the UK standard and represent profit-to-stake ratio (a $100 bet at 3/2 wins $150 profit).

Why do US sportsbooks use this format instead of decimal?

Historical convention dating to early-1900s US bookmaking. The +/- format communicates favorite/underdog status instantly without computation. The downside: comparing prices across bets (e.g. +130 vs +145) is less intuitive than 2.30 vs 2.45. Most US-licensed sportsbooks now offer a settings toggle to switch displays to decimal or fractional.

What is "even money" in American odds?

Even money is +100 (or -100, equivalent). A $100 bet wins $100 profit. Implied probability of 50%. Most sportsbooks list this as "EVEN" or "+100". Coin-flip-true 50/50 markets after vig usually price -110/-110 (each side at -110), giving the operator a ~4.5% margin built into the line.

How to Read American Odds: Complete Guide with Examples

How to Read American Odds

American odds (also called moneyline odds or US odds) use a + or − prefix to indicate underdog or favorite. They are the default format at every US-licensed sportsbook. This guide explains the format with worked examples, conversion to implied probability, and conversion to decimal and fractional formats.

The two basic shapes: + and −

Every American odds line is either a positive number (e.g. +150) or a negative number (e.g. −180). The sign tells you the favorite/underdog direction; the magnitude tells you the price.

Odds	Bet $100, win...	Risk to win $100	Implied probability	Favorite or underdog?
`+150`	$150 profit	$67	40.0%	Underdog
`+200`	$200 profit	$50	33.3%	Underdog
`+450`	$450 profit	$22	18.2%	Underdog (longshot)
`−110`	$91 profit	$110	52.4%	Slight favorite (typical "vig")
`−180`	$56 profit	$180	64.3%	Favorite
`−500`	$20 profit	$500	83.3%	Heavy favorite

Converting American odds to implied probability

Implied probability is what the price suggests the chance of winning to be. There are two formulas:

For POSITIVE odds:  probability = 100 / (odds + 100)
For NEGATIVE odds:  probability = odds / (odds + 100)

Worked examples:

+150: 100 / (150 + 100) = 100 / 250 = 40.0%
+450: 100 / (450 + 100) = 100 / 550 = 18.2%
−180: 180 / (180 + 100) = 180 / 280 = 64.3%
−110: 110 / (110 + 100) = 110 / 210 = 52.4%

Important: implied probability includes the sportsbook's margin (the vig). When you sum implied probabilities across both sides of a typical market, the total exceeds 100%. The excess is the vig — the operator's built-in edge. See our no-vig calculator to strip the vig out and compute fair-odds probability.

Why −110 is the "standard" sportsbook line

For coin-flip-close markets (most NFL spreads, NBA totals), the typical price is −110 on both sides. Each side has 52.4% implied probability. Sum: 104.8%. The 4.8% over 100% is the operator's margin — about $4.55 of every $100 bet on either side, on average, accrues to the book.

This is why a flat-bet bettor needs to win 52.4% of −110 bets just to break even, not 50%.

Converting to decimal odds

Decimal odds are the European standard and represent total return per $1 bet (including your stake).

For POSITIVE odds:  decimal = (odds / 100) + 1
For NEGATIVE odds:  decimal = (100 / odds) + 1

+150 → 1.50 + 1 = 2.50 (a $100 bet returns $250 total)
−180 → 0.556 + 1 = 1.556 (a $100 bet returns $156 total)
−110 → 0.909 + 1 = 1.909 (a $100 bet returns $191 total)

Converting to fractional odds

Fractional odds are the UK standard and represent profit-to-stake ratio.

For POSITIVE odds:  fractional = odds/100 (then simplify)
For NEGATIVE odds:  fractional = 100/odds (then simplify)

+150 → 150/100 → 3/2 (win $3 for every $2 staked)
+200 → 200/100 → 2/1 ("two-to-one")
−180 → 100/180 → 5/9 (win $5 for every $9 staked)

The mental shortcut: "magnitude tells you price"

You don't need to memorize formulas to read American odds quickly. The mental model:

Higher positive number = bigger underdog = bigger payout for $100 risked. +500 pays more than +200.
Higher negative number = bigger favorite = more $$ you must risk to win $100. −500 requires more risk than −200.
The cutoff is +100 / −100 (even money). Anything between (e.g. +110, −110) is essentially a coin flip with vig.

Common confusing edge cases

Pick'em / "EV" / "+100"

When a sportsbook lists a market as EVEN or PK (pick'em), the price is +100 on both sides — no favorite. This is rare in main markets (sportsbooks usually structure to keep the vig built in via −110/−110), but appears on some props.

Why both sides of a totals bet are usually −110

For an NBA total of 220.5, both Over and Under typically price at −110. The sportsbook isn't predicting which side will hit; it's collecting vig from both sides. Move the line, and prices shift to compensate (e.g. 220 might price Over −115 / Under −105, indicating the book takes 220.5 as fair).

How big a number can American odds get?

In practice: futures longshots can hit +50000 or higher (a 0.2% implied probability before vig, e.g. a 64-1 longshot to win the World Cup). Heavy favorites in lopsided matchups can hit −2000 or worse (95.2%+ implied). Any sportsbook displaying odds beyond these ranges is usually showing a "no bet allowed" placeholder.

How to use this in practice

The single most useful skill: looking at a price and immediately computing whether you think the true probability of the outcome is higher or lower than the implied probability. If you think the true probability is higher, the bet is +EV (positive expected value). If lower, the bet is -EV.

Use our no-vig calculator to convert two-sided market prices to fair-probability estimates. Use our parlay calculator to combine multiple American-odds legs.