Reading odds is the first skill every sports bettor needs. In this guide we explain American, decimal and fractional odds, how favorites and underdogs are priced and how to turn any price into an implied probability, so the BetOnline board can be read with confidence.
American Odds: Favorites and Underdogs
American odds use a plus or minus sign. A minus number, like -150, shows how much is staked to win $100, so the favorite costs more to back. A plus number, like +130, shows what a $100 stake returns, so the underdog pays more for the same stake. The bet slip converts this into a clear payout before confirmation.
Decimal and Fractional Formats
Decimal odds show the total return per unit staked, so 2.50 returns 2.5 times the stake including the stake. Fractional odds, common in racing, show profit against stake, so 3/1 returns three units of profit for every one staked. BetOnline lets players focus on the format that reads most easily.
Converting Odds to Implied Probability
Implied probability is the chance a price suggests. For a minus favorite, divide the odds by the odds plus 100. For a plus underdog, divide 100 by the odds plus 100. Comparing implied probability with an independent read is how sharp bettors find value on the board.
Reading a Live Odds Board
Odds move with news, money and, in live betting, the score and clock. A shortening price means more support for that side, while a drifting price means less. BetOnline keeps the confirmation step visible so a price can be locked before the market moves again.
American, Decimal and Fractional: One Price, Three Displays
The three formats look different but describe the exact same wager. A favorite shown as -150 in American odds is 1.67 in decimal and roughly 4/6 in fractional, and every one of those returns the same money on a winning bet. American odds are built around a $100 reference stake, decimal odds are built around the total return per $1, and fractional odds separate profit from stake. Once that reference point is clear, switching between them on the BetOnline board becomes a matter of preference rather than a barrier to placing a bet.
Take a straightforward underdog at +130. In American terms a $100 stake returns $130 in profit, or $230 in total. The decimal version is 2.30, because 2.30 times the stake gives the full return including the stake back. The fractional version is 13/10, since $10 staked earns $13 profit. Nothing about the payout changes; only the way the number is written down changes.
Converting Between the Three Formats
A few reliable steps handle any conversion, and the arithmetic stays simple:
- American plus price to decimal: divide the number by 100 and add 1. So +130 becomes 130 divided by 100, which is 1.30, plus 1, giving 2.30.
- American minus price to decimal: divide 100 by the number and add 1. So -150 becomes 100 divided by 150, which is 0.67, plus 1, giving 1.67.
- Decimal to fractional: subtract 1 and express the result as a fraction. Decimal 2.30 becomes 1.30, or 13/10.
- Fractional to decimal: divide the top by the bottom and add 1. So 3/1 becomes 3 plus 1, which is 4.00.
These conversions matter because different markets lean on different displays. Racing prices often appear in fractions, international lines lean decimal, and North American sportsbooks lead with American odds. Reading all three means never being locked out of a market that BetOnline offers in an unfamiliar style.
Favorites, Underdogs and What the Sign Really Means
The plus and minus signs carry the whole story of who is expected to win. A minus sign marks the favorite and shows the stake needed to win $100, so -200 means a $200 stake wins $100, and the larger the minus number grows the shorter the price and the heavier the favorite. A plus sign marks the underdog and shows the profit on a $100 stake, so +200 means $100 wins $200, and a larger plus number signals a longer shot with a bigger payout attached to a smaller chance.
Stake sizes do not have to match the $100 reference. On a favorite at -150, a $100 stake wins $66.67 for a total return of $166.67, because the win amount scales down from the reference in the same proportion. On an underdog at +130, a $60 stake wins $78 for a total return of $138. The BetOnline bet slip runs this calculation automatically, but understanding the ratio makes it easy to size a stake toward a target return before the slip is even opened.
Turning Any Price Into Implied Probability
Implied probability translates a price into the percentage chance the market is assigning. It is the single most useful habit for judging whether a number represents value. For a minus favorite, divide the odds by the odds plus 100. For a plus underdog, divide 100 by the odds plus 100. The result is the break-even win rate a bet needs to clear before it turns a long-run profit.
A Worked Implied-Probability Example
Consider a favorite priced at -150. The calculation is 150 divided by the sum of 150 and 100, which is 150 divided by 250, or 0.60. That price implies a 60 percent chance. Now consider an underdog at +130. The calculation is 100 divided by the sum of 130 and 100, which is 100 divided by 230, or roughly 0.435. That price implies about a 43.5 percent chance. When an independent read of a matchup lands meaningfully above the implied number, the price points toward value, and that gap is what sharp bettors on the BetOnline board are hunting for.
The Vig: Why a Coin Flip Is Not Priced at Even Money
A true 50-50 matchup is almost never posted at even money on both sides. Sportsbooks build in a margin, often called the vig or juice, which is the cost of making the market. The classic example is two sides both priced at -110. Each -110 implies a 52.38 percent chance, because 110 divided by 210 equals 0.5238. Add the two together and the total is 104.76 percent, even though real probabilities can only sum to 100 percent. That extra 4.76 percent is the built-in margin.
Stripping the vig back out reveals the market's true read. Dividing 52.38 by 104.76 returns 50 percent, confirming the underlying matchup is a genuine coin flip once the margin is removed. The same logic applies to lopsided markets. A favorite at -200 implies 66.7 percent and an underdog at +170 implies 37.0 percent, a total of 103.7 percent, so the margin there is 3.7 percent. Comparing the posted margin across markets shows where the pricing is tightest and where a stake stretches furthest.
Moneyline, Spread and Totals Odds
The same game usually offers three main ways to bet, and each reads its odds a little differently. A moneyline bet is a straight pick of the winner, so the odds swing widely to reflect how mismatched the teams are, from a short -300 favorite to a long +250 underdog. A point spread levels the field by adding or subtracting points, so the odds on each side sit close together, commonly around -110, with the handicap doing the work instead of the price. A total, or over/under, sets a combined score line and again prices both sides near -110, so the number itself carries the meaning.
How the Same Game Offers Three Different Bets
Imagine a matchup where one team is a clear favorite. On the moneyline that side might be -180 while the other is +155. On the spread the favorite could be laid at -3.5 priced -110, with the underdog at +3.5 also priced -110. The total might be set at 47.5 points with over and under both at -110. Three bets, one game, and three separate ways to express a view, all visible together on the BetOnline board so the most confident angle can be chosen. Bettors weighing more than one of these at once can read the same game parlays explained guide at /blog/same-game-parlays-explained/ to see how selections from a single game combine.
How Odds Move and Why
Prices are not fixed once posted. They drift and shorten as money arrives, as news breaks and, during a game, as the score and clock change. A price that shortens, for example from +150 to +130, signals growing support for that side, while a price that drifts from -110 to +105 signals the opposite. Injury reports, lineup confirmations, weather and heavy stakes on one side all push the number. Following these moves across the day builds an instinct for when a price is likely to be at its best. Markets that update fastest sit on the /live-betting/ page, where odds shift map by map, drive by drive and minute by minute.
Line Shopping: Small Edges That Add Up
Two prices for the same outcome are not always equal, and the better one wins more money for the same risk. A side offered at -105 rather than -110 returns slightly more on every winning bet, and over hundreds of wagers that small difference compounds into a meaningful edge. The same applies to catching an underdog at +145 instead of +135, or a total that has moved half a point in a favorable direction. Checking the number before confirming, and knowing what a fair price looks like from the implied-probability math above, is the most repeatable habit a bettor can build. The full range of markets to compare sits on the /sports/ hub.
Putting the Board Into Practice
Reading odds well is less about memorizing tables and more about a short routine: identify the favorite and underdog from the sign, convert the price to an implied probability, note the margin baked into the two sides, and compare the number against an independent read before committing a stake. New markets such as esports carry the same logic in a different setting, covered in the beginner guide at /blog/esports-betting-for-beginners/. Loyal players can also review how sustained activity is recognized on the /vip-rewards/ page, and the wider library of explainers lives at /blog/. With the fundamentals in place, every price on the BetOnline board becomes a number that can be read, questioned and acted on with confidence. 21+, bet responsibly.