Sports Betting Odds Explained: Moneyline, Spreads, Over/Under & Parlays
2026-05-18 — algopicksai-sportsbook
If you have ever placed a sports bet — or tried to — you have run into a wall of numbers: -110, +150, -7.5, 48.5. These are not random. They are a language, and once you can read them, every bet type becomes straightforward. This guide decodes that language from the ground up.
We will cover every major odds format used by US sportsbooks: American odds notation, moneyline bets, point spread bets, over/under totals, and parlays. Each section includes concrete worked examples with real dollar amounts so you can see exactly how payouts are calculated — and why the math matters before you put money down.
No picks. No strategy. Just the mechanics, explained clearly.
How American Odds Work
American odds are the default format on every major US sportsbook — DraftKings, FanDuel, BetMGM, and the rest. They use a plus (+) or minus (–) prefix to communicate two things simultaneously: which side is favored, and how much you stand to win or lose relative to a fixed stake.
The minus sign (–) marks the favorite. A -150 line means you must risk $150 to win $100 in profit. The favorite is more expensive to bet because the sportsbook's model gives them a higher probability of winning.
The plus sign (+) marks the underdog. A +130 line means a $100 risk wins $130 in profit. Underdogs pay out more per dollar risked because they are less likely to win.
Pick'em (+100 / even odds): When both sides are evenly matched, the line sits near +100 on both sides — risk $100 to win $100.
Here is how three common lines translate to real dollar amounts:
| Odds | $100 Bet Returns | $100 Bet Profit | $50 Bet Profit |
|---|---|---|---|
| -110 | $190.91 | $90.91 | $45.45 |
| +110 | $210.00 | $110.00 | $55.00 |
| +200 | $300.00 | $200.00 | $100.00 |
The reason most lines are set at -110 rather than even (-100 / +100) is the vig — the sportsbook's built-in margin. We will return to that concept in the Implied Probability section.
Moneyline Odds
A moneyline bet is the simplest bet in sports betting: you pick which team wins outright. No points, no margin — just win or lose.
Worked example: Bills vs Jets
Suppose the Bills are listed at -165 and the Jets at +140.
- Bills -165 (favorite): To win $100 in profit, you must risk $165. If the Bills win by any margin — 1 point, 30 points — your bet pays out $265 total ($100 profit + your $165 stake returned).
- Jets +140 (underdog): A $100 risk wins $140 in profit ($240 total return) if the Jets win the game outright.
Notice the gap between -165 and +140. A perfectly balanced market with no sportsbook margin would sit at roughly -140/+140. The gap between -165 and +140 represents the sportsbook's edge — you are paying more to back the favorite than you receive for backing the underdog.
When moneylines are most useful
Moneylines are especially common in lower-scoring sports where point spreads are impractical or narrow:
- Baseball: A 1–0 game is common. A -1.5 spread (the "run line") exists but many bettors prefer the cleaner moneyline.
- Hockey: Games are frequently decided by one goal. The puck line (+/- 1.5) exists, but moneylines are heavily traded.
- Soccer: Three outcomes (win, draw, loss) mean soccer markets are often bet as three-way moneylines.
The large-favorite problem
Heavy favorites create a math problem for bettors. A team listed at -400 requires you to risk $400 to win $100 in profit. If that team wins, you collect $500 total — a 25% return on risk. If they lose even once, you need four wins to recover. Large favorites are not "safe" bets; they simply cost more per unit of profit.
Point Spread Odds
The point spread levels the playing field between mismatched teams by requiring the favorite to win by a specific margin. Instead of betting who wins, you are betting by how much they win or lose.
Worked example: Chiefs vs Raiders
The line is posted as: Chiefs -7.5 (-110) vs Raiders +7.5 (-110)
- Chiefs -7.5: The Chiefs must win by 8 or more points for this bet to pay out. A 24–17 Chiefs win (margin of 7) loses the spread bet even though the Chiefs won the game.
- Raiders +7.5: The Raiders bet wins if the Raiders win outright, OR if they lose by 7 or fewer points. A 24–17 Chiefs win means the Raiders covered the +7.5 because they lost by exactly 7 — which is less than 7.5.
Both sides are priced at -110, meaning each requires $110 to win $100. That -110 on both sides is the vig.
Covering the spread
"Covering the spread" simply means winning your spread bet. If you bet the Chiefs -7.5 and they win by 10, the Chiefs "covered." If they win by 6, they failed to cover even though they won the game.
Half-point spreads eliminate pushes
Spreads ending in .5 (like -7.5) are intentional. A whole-number spread (Chiefs -7) creates a push — if the Chiefs win by exactly 7, all bets are returned with no winner. Sportsbooks prefer half-point lines to force a decisive outcome on every ticket.
Line movement
When a line is first posted, it reflects the sportsbook's initial probability estimate. As bets come in, the line adjusts to balance action. If a large amount of money floods in on the Chiefs, the line might move from Chiefs -7.5 to Chiefs -8.5 to incentivize Raiders betting and distribute the sportsbook's liability. Tracking line movement tells you something about where sharp money is going.
Over/Under (Totals) Odds
An over/under bet (also called a totals bet) removes teams entirely. Instead of picking a winner, you are predicting whether both teams combined will score more or fewer points than the posted total.
Worked example: NFL total set at 48.5
- Over bet: Wins if both teams combine for 49 or more points. Example: a 28–21 final gives a combined score of 49 — the Over wins.
- Under bet: Wins if both teams combine for 48 or fewer points. A 24–21 final (combined 45) — the Under wins.
- Standard pricing: -110 on both sides. A $110 Over bet on that 28–21 game returns $210 ($100 profit + $110 stake).
Factors that move totals
- Weather: Rain and wind suppress scoring in outdoor football games. When a forecast calls for sustained 20+ mph winds at an outdoor stadium, sharp money frequently hammers the Under.
- Pace and tempo: High-pace NBA teams produce high-scoring games; slow, defense-first teams do not. The total reflects expected pace.
- Injuries to key offensive players: A missing starting quarterback, point guard, or pitcher dramatically affects scoring expectation.
Totals across sports
The total type varies by sport. NFL totals typically range from the low 40s to mid-50s. NBA games commonly total 220–235 points. NHL totals are typically 5.5 or 6.5 goals — not 48.5. Soccer totals are usually 2.5 goals. The structure is the same; only the scale changes.
Parlay Odds
A parlay combines two or more individual bets (called legs) into a single wager. All legs must win for the parlay to pay out. If even one leg loses, the entire parlay loses.
The trade-off: parlays pay out significantly more than winning each bet individually — but the probability of winning decreases with every leg added.
How parlay payouts are calculated
Each leg's American odds are converted to a decimal multiplier, then all multipliers are multiplied together.
To convert American odds to decimal:
- Negative odds: decimal = (100 / |odds|) + 1. Example: -110 → (100/110) + 1 = 1.909
- Positive odds: decimal = (odds / 100) + 1. Example: +150 → (150/100) + 1 = 2.500
Worked example: 3-leg parlay, all legs at -110
Each leg decimal = 1.909
Total multiplier: 1.909 × 1.909 × 1.909 = 6.957
A $100 parlay bet at this multiplier returns approximately $696 total ($596 profit).
Compared to winning three separate -110 bets for $100 each, you would net three separate profits of ~$91 each = $273 total. The parlay pays roughly twice as much — but requires all three to land.
Multi-leg payout table (all legs at -110)
| Legs | Approx. Total Return on $100 | Approx. Profit |
|---|---|---|
| 2 | $264 | $164 |
| 3 | $596 | $496 |
| 4 | $1,228 | $1,128 |
| 5 | $2,343 | $2,243 |
Why each leg matters so much
Adding a leg does not just add difficulty linearly — it multiplies it. If each leg has a 50% win probability (roughly even odds), a 2-leg parlay wins 25% of the time; a 4-leg parlay wins only 6.25% of the time. The bigger the parlay, the rarer the win — which is why the payouts are so large.
Same-game parlays (SGPs)
A same-game parlay combines multiple bets from within a single game — for example, Chiefs to win, Patrick Mahomes to throw for 300+ yards, and Travis Kelce to score a touchdown. Because these legs are correlated (Mahomes throwing 300 yards makes a Chiefs win more likely), sportsbooks adjust the odds downward to account for the correlation. SGP payouts are lower than combining equivalent legs from unrelated games.
Implied Probability
Every set of odds has an implied probability — the win likelihood that the line is pricing in. Understanding this number lets you compare your own assessment against the sportsbook's.
The formula
-
For negative odds: implied probability = |odds| / (|odds| + 100)
- -110: 110 / 210 = 52.4%
- -165: 165 / 265 = 62.3%
-
For positive odds: implied probability = 100 / (odds + 100)
- +130: 100 / 230 = 43.5%
- +200: 100 / 300 = 33.3%
The vig gap
On a standard -110 / -110 line, both sides carry a 52.4% implied probability. Add them: 52.4% + 52.4% = 104.8%. A real-world probability set must sum to 100%. The excess 4.8% is the sportsbook's margin — the vig. No matter which side wins, the book profits because it priced both sides above true 50%.
Practical use: identifying perceived value
If you believe a team has a 60% chance of winning but the line prices them at 52.4% implied probability, you perceive an edge — the line is undervaluing them relative to your estimate. This is the core concept behind "value betting": finding lines where the sportsbook's implied probability is lower than your assessed true probability. This is harder than it sounds, but understanding implied probability is the first step.