How Betting Odds Work
Betting odds tell you two things at once: how likely the sportsbook thinks an outcome is, and how much you get paid if it happens. In the United States, most sportsbooks — bet365, DraftKings, FanDuel, BetMGM, Caesars and the rest — show American odds by default, written with a plus or minus sign like +150 or -180. This guide explains how to read those numbers, convert them to decimal and fractional formats, work out your exact payout, and spot how much the book is charging you through the built-in margin.
American (moneyline) odds: what the + and − mean
American odds are quoted around a $100 baseline.
- A minus number (e.g. -180) is the favorite. It tells you how much you must stake to win $100. At -180 you risk $180 to win $100.
- A plus number (e.g. +150) is the underdog. It tells you how much you win on a $100 stake. At +150 a $100 bet wins $150.
The closer the number is to even (around +100 / -100), the closer the two sides are in the book's estimation. A big favorite like -400 pays little; a longshot like +650 pays a lot because it is judged unlikely.
Worked example: You bet $50 on an NBA team at +130. Profit = $50 × (130 / 100) = $65. Your account returns $115 total (your $50 stake plus $65 profit). If instead the team is priced -130, profit = $50 × (100 / 130) = $38.46, for a $88.46 return.
Converting American odds to decimal and fractional
Some markets and international competitions (Champions League, Serie A, ATP Tour) are easier to compare in decimal odds, and older guides use fractional. All three describe the same price.
Decimal odds show your total return per $1 staked, including the stake. Formulas: - Positive American to decimal: (odds / 100) + 1. So +150 = 2.50. - Negative American to decimal: (100 / odds) + 1. So -180 = 1.556.
Decimal to payout is simple: stake × decimal odds = total return. A $40 bet at 2.50 returns $100.
Fractional odds show profit relative to stake. +150 becomes 3/2 (win $3 for every $2). -180 becomes roughly 5/9. Fractional is less common on US sportsbooks but still turns up on futures and horse-style markets.
Quick reference: - +200 = 3.00 decimal = 2/1 fractional - +100 = 2.00 decimal = 1/1 (even money) - -150 = 1.667 decimal = 2/3 fractional - -200 = 1.50 decimal = 1/2 fractional
Odds Converter
Turning odds into implied probability
Every price contains an implied probability — the chance the outcome must have for the bet to break even.
- Negative American odds: probability = odds / (odds + 100). So -180 implies 180 / 280 = 64.3%.
- Positive American odds: probability = 100 / (odds + 100). So +150 implies 100 / 250 = 40%.
This is the single most useful skill for a bettor. If you think an NFL underdog priced at +150 (40% implied) actually wins 45% of the time, the price offers value. If you think it wins only 35% of the time, the price is too short and you pass.
Worked example: An MLB moneyline shows one side at -140 and the other at +120. Implied probabilities are 140/240 = 58.3% and 100/220 = 45.5%. Those add up to 103.8%, not 100%. The extra 3.8 percentage points is the sportsbook's margin — explained next.
The sportsbook margin (the "juice" or vig)
A fair coin flip would be priced at +100 on both sides (2.00 decimal each), summing to exactly 100% probability. Real markets price both sides so the total exceeds 100%. That overround is how the book makes money regardless of result.
We sample live prices across US sportsbooks to estimate the average margin each one builds into two-way markets. Lower is better for you, because tighter margins mean you keep more of a winning edge over time. From our sampled data:
- Fanatics Sportsbook — average margin 4.25% (466 markets sampled)
- DraftKings — 4.25% (1,068 sampled)
- FanDuel — 4.46% (596 sampled)
- BetMGM — 5.21% (438 sampled)
- Caesars Sportsbook — 5.27% (906 sampled)
- BetRivers — 6.35% (480 sampled)
These are editorial estimates from price samples, not a guarantee for every market. On a single wager the difference looks small, but on hundreds of bets a 4.25% margin book meaningfully outperforms a 6.35% one for the same betting skill.
Worked example of margin cost: On a market with 4.25% margin you might see -105 on both sides. On a 6.35% market the same true 50/50 event might be priced -113 both ways. To win $100 you'd risk $105 at the tighter book versus $113 at the wider one — an extra $8 of stake at risk for the identical outcome.
Best price share: who prints the top number
Margin measures a book's whole market. Best price share measures how often an operator posts the single best available price on a market compared with rivals we track. If you shop lines, a higher best-price share means that book more often gives you the top payout.
From our sampled comparisons:
- DraftKings led the best-price share at about 54% of sampled markets.
- Fanatics Sportsbook was next around 42%.
- FanDuel and Caesars both landed near 36%.
- BetRivers around 28%, BetMGM around 20%.
Editorial read: DraftKings and Fanatics combine competitive margins with a high best-price share, which is why DraftKings carries an odds rating of 7.9 and Fanatics 7.4 in our scoring, while bet365 leads the overall odds rating at 8.8 on the strength of market coverage (9.6) and depth. If price is your priority, comparing at least two of these before you place a bet is worth the extra minute.
Reading odds across different bet types
The same odds logic applies whether you bet a moneyline, spread, total or parlay.
- Moneyline: straight pick of the winner, priced as above.
- Point spread: a handicap (e.g. -6.5) that usually sits near -110 on each side. The -110 is where the margin lives.
- Totals (over/under): also typically priced around -110 either way.
- Same Game Parlay / parlays: combine multiple selections. Decimal is easiest here — multiply the decimal odds of each leg. Three legs at 1.91, 2.10 and 1.75 give 1.91 × 2.10 × 1.75 = 7.02 decimal, so a $20 SGP returns about $140. Parlays multiply your payout but also multiply the margin, which is why they are lucrative for the book.
- Live betting: prices move as the game unfolds; the same reading rules apply, just faster.
Cash Out lets you settle early at a price the book calculates from current odds — useful for locking profit, but it bakes in extra margin, so you rarely get the full theoretical value.
Odds are set by state-licensed operators
US sports betting is regulated state by state. An operator licensed by the New Jersey DGE is not automatically legal in New York, Pennsylvania, Michigan, Colorado, Ohio, Illinois, Arizona, Virginia or Massachusetts — each has its own regulator, and the minimum age is 21. The odds and markets you see, and the payment methods available (PayPal, Venmo, Apple Pay, Online Banking, Visa, Play+), depend on your state.
That matters for line shopping: the set of books competing for the best price differs by state, so which operator prints the top number on a given night depends partly on who is live where you are. Our verification is limited to licence and register status — confirm any operator is authorized by your own state regulator before depositing.
FAQ
What do + and − mean in betting odds?
A minus sign marks the favorite and shows how much you must stake to win $100 (e.g. -180 = risk $180 to win $100). A plus sign marks the underdog and shows how much you win on a $100 stake (e.g. +150 = win $150 on $100).
How do I convert American odds to decimal?
For positive odds, divide by 100 and add 1: +150 becomes 2.50. For negative odds, divide 100 by the number and add 1: -180 becomes 1.556. Then multiply your stake by the decimal figure to get your total return including stake.
How do I calculate my payout?
In decimal, stake × odds = total return. A $40 bet at 2.50 returns $100 ($60 profit). In American odds at +130, a $50 bet profits $50 × 130/100 = $65; at -130 it profits $50 × 100/130 = $38.46.
What is the vig or juice?
It's the sportsbook's margin — the reason two-way market probabilities add up to more than 100%. A -140 / +120 baseball moneyline implies 58.3% + 45.5% = 103.8%, so about 3.8% is margin. Lower-margin books, such as those we sampled around 4.25% (Fanatics, DraftKings), leave more value for winning bettors than higher ones near 6.35% (BetRivers).
Why do the same odds differ between sportsbooks?
Each book prices its own view and margin, so payouts vary. In our sampling DraftKings posted the best available price on about 54% of markets and Fanatics on about 42%. Comparing two or three books before betting can raise your payout on the same outcome.
Does implied probability tell me the true chance?
No. Implied probability is the book's price stripped of format, not a guarantee. It also includes margin, so real market probabilities are slightly lower than the raw figures suggest. Your edge comes from finding outcomes you rate more likely than the price implies.