Sportsbook Betting Explained: How odds, spreads, and lines work

Sportsbook Betting Explained: Sports betting in the United States has grown rapidly since legalization began in 2018. Millions of new bettors are signing up at online sportsbooks, eager to place wagers on the NFL, NBA, MLB, NHL, and college sports. But while the excitement is real, many newcomers find the numbers on sportsbook screens confusing.

What does -110 mean? Why do some teams have +7.5 spreads while others don’t? And what exactly is the difference between moneyline, point spread, and totals? Understanding how sportsbooks set odds, spreads, and lines is the foundation of betting smarter.

Also Read: What is a Sportsbook? Here’s a beginner’s guide to US online sports betting

In this guide, we’ll break down how sportsbooks work, explain the main types of bets, and show you how odds are calculated. By the end, you’ll be able to read sportsbook lines with confidence and spot value where others see only numbers.

Sportsbook Betting Explained: What is a sportsbook?

A sportsbook is a platform—online or in-person—that accepts bets on sports events. Sportsbooks don’t just offer simple win-or-lose wagers; they set markets that include spreads, totals, props, parlays, and futures.

The goal of a sportsbook is not to predict outcomes perfectly but to set odds in a way that encourages balanced betting on both sides. That way, the book earns a margin (called the vig or juice) regardless of the result.

Understanding odds

Odds show how much you can win on a bet. In the US, sportsbooks use American odds:

• Favorites: Marked with a minus sign (-). Example: -150 means you need to bet $150 to win $100.
• Underdogs: Marked with a plus sign (+). Example: +200 means a $100 bet would win $200 profit.

Odds reflect both the probability of an outcome and the demand from bettors. If heavy money comes in on one side, sportsbooks may adjust odds to balance action.

Also Read; Top 10 Online Sportsbooks for Safe & Secure Betting in 2025

How point spreads work

Point spreads are used to even the playing field between mismatched teams. Instead of simply betting on who wins, you bet on the margin of victory.

• Example: Kansas City Chiefs -7.5 vs New York Jets +7.5
  • Chiefs must win by 8 points or more to cover.
  • Jets can win outright or lose by 7 points or fewer to cover.

Spreads usually carry odds of -110, meaning you bet $110 to win $100. This is where sportsbooks collect their margin.

How totals (over/under) work

Instead of picking a side, you can bet on the total points scored in a game.

• Example: Over/Under 48.5 in an NFL game
  • Over bettors win if the combined score is 49 or more.
  • Under bettors win if the combined score is 48 or fewer.

Totals are popular because you don’t need to predict the winner—just the pace of the game.

How moneylines work

The moneyline is the simplest form of bet: pick the outright winner.

• Example:
  • New England Patriots +150
  • Dallas Cowboys -180

A $100 bet on the Patriots would return $150 profit if they win. A $180 bet on the Cowboys would return $100 profit if they win.

Moneylines are common in MLB, NHL, and underdog-heavy games where spreads aren’t as attractive.

How sportsbooks set lines

Sportsbooks use a mix of:

• Statistical models
• Team and player performance data
• Public perception and betting volume
• Situational factors (injuries, weather, travel schedules)

Lines open at one number but often move as betting action flows in. This is why monitoring line movement is key for sharp bettors.

Key takeaways for US bettors

1. Learn to read odds: Understand favorites and underdogs in American odds format.
2. Spreads balance teams: Don’t just look at the winner—focus on margins.
3. Totals focus on pace: Useful when teams have contrasting offensive and defensive styles.
4. Lines move with money: Watch market shifts to identify sharp action.
5. The vig is real: Sportsbooks always build in their margin—factor it into your betting strategy.

FAQs

Q1: What does -110 mean in sportsbook odds?
It means you need to wager $110 to win $100 profit. The extra $10 is the sportsbook’s margin.

Q2: Why do sportsbooks change lines after they’re posted?
Lines move to balance action. If too much money is on one side, the book adjusts to encourage bets on the other.

Q3: What’s the difference between moneyline and spread?
Moneyline bets are on who wins the game outright. Spread bets are on the margin of victory.

Q4: Can sportsbooks lose money if everyone bets one side?
Yes, but they adjust odds and limits to minimize that risk. Their business model is built around managing balance, not predicting perfectly.

Q5: Which is better for beginners: moneyline, spread, or total?
Many beginners start with moneylines because they’re straightforward. Spreads and totals require more nuance but can offer better long-term value.