Learn to read sports betting lines in under 2 minutes. Covers favorite vs. underdog, moneyline odds, spreads, and calculating your payout.
You open your app and see this line:
Kansas City Chiefs -3.5 (-110) vs. Philadelphia Eagles +3.5 (-110)
Three numbers, three things to understand. Here is how to read all of them in about two minutes.
Every betting line uses American odds format. The sign in front of the number is your first clue:
Think of it this way: negative means you pay more to win less (the book expects this outcome). Positive means you pay less to win more (the book thinks this is less likely).
You do not have to bet exactly $100. The formulas scale to any stake:
For a favorite at -150 with a $50 stake:
For an underdog at +130 with a $50 stake:
Tip: Skip the math entirely. Use the Single Bet Calculator — enter any odds and stake, and it shows your profit, total return, and implied probability instantly.
The spread levels the matchup between two unevenly matched teams. In our example:
The half-point (3.5 instead of 3) eliminates pushes — there is no tie. You either win or lose the bet.
Real scenario: If the Chiefs win 27-24 (a 3-point margin), a bet on Chiefs -3.5 loses because they did not cover. A bet on Eagles +3.5 wins because the Eagles lost by fewer than 3.5 points.
Notice both sides of the spread are priced at -110. That is the vig (short for vigorish) or juice — the sportsbook's built-in fee.
At -110, you risk $110 to win $100. Add up the implied probabilities and you see the book's edge:
That 4.76% above 100% is the sportsbook's profit margin. Your break-even win rate at -110 is 52.38% — you need to win more than half your bets just to cover the vig.
Tip: Not all sportsbooks charge the same juice. Some offer -105 on spreads. Shopping lines across 2-3 books is the simplest way to cut the vig you pay over time. Even a small difference from -110 to -105 adds up over hundreds of bets.
When you see Chiefs -3.5 (-110), you now know three things:
Enter -110 into the Single Bet Calculator with your usual stake and see the exact payout. Then use the Odds Converter to see that -110 equals 1.909 decimal, 10/11 fractional, and 52.38% implied probability.
For a deeper look at how the vig works and how to remove it, see the No-Vig Calculator guide.
A negative number (like -150) means that team is the favorite. You risk that amount to win $100 profit. -150 means risk $150 to win $100.
A positive number (like +130) means that team is the underdog. A $100 bet wins $130 profit.
The spread is a margin of victory the favorite must exceed. If a team is -3.5, they must win by 4 or more for a bet on them to pay out.
The vig is the sportsbook's fee built into the odds. Standard juice on spread bets is -110, meaning you risk $110 to win $100.