Why Understanding Odds Matters
Sports betting odds tell you two things at once: how likely an outcome is and how much you stand to win. Every bet you place — from NFL moneylines to NBA point spreads — is priced in one of three odds formats. Understanding how each format works lets you compare lines across sportsbooks, calculate potential payouts before risking your bankroll, and identify value bets where the implied probability is lower than the real chance of winning. Whether you use BetOnline or any other sportsbook, odds literacy is the single most important skill for any bettor.
Decimal Odds
Decimal odds are the simplest format and the default in most of Europe, Australia and Canada. The number shown is your total return per $1 staked — profit plus original stake combined. For example, decimal odds of 2.50 mean a $100 bet returns $250 total ($150 profit + $100 stake). The formula is straightforward: stake × decimal odds = total payout. To find profit alone, subtract your stake from the total: $250 − $100 = $150 profit. Lower decimal numbers indicate the favourite; higher numbers indicate the underdog. Decimal odds of 1.50 represent a strong favourite, while 3.50 suggests a clear underdog. Decimal format is popular because the math is instant — no subtraction needed to compare two prices side by side.
Fractional Odds
Fractional odds are the traditional format used in the UK and Ireland, common in horse racing and football betting. Written as a fraction like 5/2 or 3/1, the first number is your profit and the second is your stake. So 5/2 means you win $5 for every $2 staked — a $100 bet at 5/2 returns $350 total ($250 profit + $100 stake). Even-money odds appear as 1/1 (or "evens"), meaning you win exactly what you stake. Long shots might show as 10/1 or 20/1. Fractional odds can be tricky for quick comparisons because the fractions need to be mentally converted to decimals. Most modern bettors convert fractional to decimal mentally: 5/2 = 2.5, 3/1 = 4.0, 10/1 = 11.0.
American Odds
American odds (also called moneyline odds) are the default format at US sportsbooks like BetOnline. They use a plus/minus system: positive numbers show your profit on a $100 bet, while negative numbers show how much you need to stake to win $100. For example, +150 means a $100 bet profits $150 (total return $250). A line of -110 means you must risk $110 to win $100 in profit (total return $210). The further negative a number goes (-200, -300, -400), the bigger the favourite. The further positive (+200, +300, +400), the bigger the underdog. American odds are intuitive once you understand the $100 baseline — they tell you instantly who the market favours and exactly how much you win per $100 wagered.
How to Calculate Payouts
Each format requires a slightly different calculation. For decimal odds, multiply your stake by the decimal number: $50 × 2.50 = $125 total return ($75 profit). For fractional odds of 3/1, multiply your stake by the fraction: $50 × (3/1) = $150 profit, plus your $50 stake = $200 total. For American odds, positive odds use: (stake × odds) / 100 = profit. So $50 at +150 = ($50 × 150) / 100 = $75 profit. Negative odds use: (stake / |odds|) × 100 = profit. So $50 at -110 = ($50 / 110) × 100 = $45.45 profit. Most sportsbooks display potential payouts automatically in the bet slip, but knowing the math helps you verify the numbers and shop for the best line.
Value Betting
Value betting is the practice of finding odds where the sportsbook's implied probability is lower than the actual probability of the outcome winning. Every set of odds implies a probability: decimal odds of 2.0 imply 50%, American -200 implies 67%, and so on. When your own assessment of the probability is higher than the sportsbook's implied probability, a value bet exists. For example, if a team is priced at +150 (implied 40% probability) but you believe they have a 55% chance of winning, there is value in the bet. Over a large sample, value betting is the only sustainable path to long-term profit. Sharp bettors compare odds across multiple sportsbooks to find discrepancies — even a 5-cent difference between -110 and -105 on the same line adds up over hundreds of bets.
Odds Comparison Across Sportsbooks
No single sportsbook offers the best odds on every market. Line shopping — comparing the same bet across multiple sportsbooks — is how professional bettors squeeze out extra value. For NFL games, one sportsbook might offer a team at +3.5 while another has them at +3.0 with a better price (-105 instead of -110). For NBA totals, one book might post 220.5 at -110 while another offers 219.5 at -110 — the half-point difference matters. Always have accounts at more than one sportsbook so you can check lines before placing your bet. BetOnline posts competitive American odds across NFL, NBA, MLB and NHL markets, but comparing with other books before clicking "place bet" is a habit that pays over time.
Implied Probability Cheat Sheet
Every odds number maps to a percentage. Decimal 2.00 = 50%. Decimal 1.50 = 67%. Decimal 3.00 = 33%. American -150 = 60%. American +200 = 33%. American +300 = 25%. Use this formula: implied probability = 1 / decimal odds × 100. For American odds, positive: 100 / (odds + 100) × 100; negative: |odds| / (|odds| + 100) × 100. Knowing implied probability lets you quickly judge whether a line offers value or is overpriced. Sportsbooks bake a margin (the "vig" or "juice") into every line, so the combined implied probabilities of both sides will always exceed 100% — typically around 104-108%. Understanding vig helps you see why line shopping matters: lower vig means better value on every bet.