// The Basics

How to read
a betting line.

Most betting content assumes you already know this. This page doesn't. It covers what the numbers mean, what they cost you, and which of them actually predict whether someone knows what they're doing — in plain English, with the arithmetic shown rather than hidden.

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Reading the odds

American odds look strange until you know the trick: the number is always relative to $100, and the sign tells you which direction.

• Negative (-150) — how much you must risk to win $100. At -150 you stake $150 to win $100.
• Positive (+150) — what $100 wins. At +150 a $100 stake returns $150 profit.

A negative number means the favorite; positive means the underdog. The bigger the number in either direction, the more lopsided the matchup is priced.

Decimal odds (common outside the US) are cleaner: they show total return per $1 staked, so 1.50 means $1 comes back as $1.50. Our converter moves between all four formats.

The three main markets

Moneyline

The simplest bet: pick who wins. No margin, no handicap. Price does all the work — a heavy favorite pays badly, an underdog pays well.

Spread (or run line, puck line)

The favorite gives up points; the underdog receives them. Chiefs -6.5 means Kansas City must win by seven or more for the bet to land. This exists to make lopsided games bettable on both sides at roughly even money.

Total (over/under)

A single number for combined score. You bet whether the real total lands above or below it. You're betting on the game's shape, not on who wins — which makes totals attractive when you have a read on pace, weather or pitching but no strong opinion on the winner.

The vig — what the bookmaker charges

A coin flip should pay +100 on both sides. It doesn't. It pays about -110 each way, and that gap is the sportsbook's fee — the vig (also juice, or hold).

Here's the arithmetic. At -110, the implied chance is 52.4%. Both sides together come to 104.8%. That extra 4.8 points is the house's margin, and it's why beating sports betting is hard: you're not trying to beat 50/50, you're trying to beat 52.4%.

This is why line shopping matters. The same game priced -105 instead of -110 at another book is a permanent, guaranteed improvement to every bet you make.

Implied probability and no-vig prices

Every price converts to a percentage — the chance the market is assigning. But raw implied probabilities always total more than 100%, because the vig is baked in. To see what the market really thinks, you strip it out.

Take a game priced -138 / +116. Raw implied: 58.0% and 46.3%, totalling 104.3%. Divide each by that total and you get 55.6% and 44.4% — the market's true read, and now it sums to 100 as a probability should.

Closing line value — the metric that actually matters

Win rate over a short run tells you almost nothing. Twenty bets is noise; a bad handicapper can go 12-8 by luck and a good one can go 8-12.

Closing line value is the better test. If you bet a team at +150 and the line closes at +130, you got a better price than the final market consensus — you had CLV, regardless of whether the bet won. The closing line is the sharpest number the market produces, because it reflects every bit of money and information right up to kickoff.

• Consistently beating the close means you're finding value before the market corrects.
• It shows up in far fewer bets than win rate needs, because it isn't hostage to variance.
• It's very hard to fake. Anyone can cherry-pick winners; the closing line is a matter of public record.

If you're evaluating whether to trust a service, this is the question worth asking — and the one almost none of them answer.

Units and staking

A unit is one standard bet, expressed as a percentage of bankroll rather than a dollar figure. Most disciplined bettors use 1–3%. It lets people compare results honestly without disclosing what they actually wager.

Flat staking — the same size on every play — beats chasing. The impulse to double after a loss is the fastest route to a ruined bankroll, because losing runs are longer than intuition suggests.

A ten-bet losing run is completely normal for a profitable bettor. Size so it's survivable, not so it's lucrative if you never lose. Kelly staking formalises this by scaling stake to edge.

Common mistakes

• Judging on win rate alone. At -110 you need 52.4% just to break even. A 55% win rate is excellent; 51% loses money.
• Ignoring the price. Being right about who wins isn't enough if you paid too much to be right.
• Parlays as a staple. The vig compounds with every leg. A four-leg parlay of -110s carries a far higher effective hold than four singles.
• Chasing losses. Raising stakes after a loss converts a normal downswing into a terminal one.
• Betting your fandom. The team you watch most is the team you're least objective about.
• One book. Not shopping lines is a permanent tax on every bet you place.

Glossary