How to bet on sports: a beginner’s guide

Every bet is priced in odds, and odds do two jobs at once: they tell you the payout and they imply a probability. American odds are written with a plus or minus. A minus number (e.g. -150) is the favorite and shows how much you must stake to win 100; a plus number (e.g. +130) is the underdog and shows how much you win on a 100 stake. The bigger the minus, the heavier the favorite.

Convert odds to an implied probability and you can judge whether a price is fair. -150 implies roughly a 60% chance; +130 implies about 43%. Notice those add up to more than 100% — the extra is the sportsbook’s margin, called the vig or juice. Learning to strip the vig out and read the “no-vig” fair price is the first real skill in betting.

Moneyline: pick who wins, straight up. Simple, but favorites pay little and underdogs carry real risk. Spread: the favorite must win by more than a set margin (e.g. -6.5) while the underdog can lose by fewer points or win outright — this balances mismatched teams to roughly a coin flip. Total (over/under): bet whether the combined score lands above or below a posted number, independent of who wins.

Beyond these sit props (outcomes within a game, like a player’s points or strikeouts), futures (season-long markets like a championship), and parlays (multiple bets combined for a bigger payout that only cashes if every leg wins). Beginners should master the three core markets before touching parlays — the long-shot payouts are tempting but carry a much larger built-in margin.

Open accounts at two or three licensed sportsbooks in your state, deposit only money you can afford to lose, and start with small, flat stakes — one “unit” equal to about 1% of your bankroll per bet. Find the game, choose a market, confirm the price, and the slip shows your potential payout before you submit.

Having more than one book matters more than it sounds: the same game is priced slightly differently everywhere, and always taking the best available number — line shopping — is the single easiest edge a recreational bettor can capture.

Bet a consistent unit size instead of chasing losses with bigger wagers. Shop for the best line every time. Track your bets so you know your real record, not your remembered one. And judge your process by whether you’re beating the closing line, not by a hot or cold week — short-run results are mostly variance.

Above all, treat betting as entertainment with a cost, not an income plan. The math favors the house on the average bet; a disciplined bettor’s whole job is to find the few prices that are wrong and bet them at the right size. If it stops being fun, step away — and if you ever feel out of control, call 1-800-GAMBLER.

Convert both sides to implied probabilities, then divide each by their total. Take a game priced at -150 and +130. The favorite implies 150 / 250 = 60.00%, and the underdog implies 100 / 230 = 43.48%. Together they sum to 103.48%; the extra 3.48 points is the vig.

Divide each side by 1.0348 to remove it. The favorite becomes 57.98% and the underdog 42.02%. As American odds, that is roughly -138 and +138.

The fair price tells you what a bet needs. If you think the underdog wins 45% of the time, +130 is worth a look, since it needs 43.48%. If you think 42%, the price is close to fair, and the vig makes it a small losing bet.

Decimal odds show the total return for each 1 staked, including the stake. A price of 2.30 returns 2.30 on a winning stake of 1, which is 1.30 of profit. That is the same as +130 in American odds.

Converting is simple. For plus odds, divide by 100 and add 1: +130 becomes 2.30. For minus odds, divide 100 by the number and add 1: -150 becomes 1.67 and -110 becomes 1.91. The implied probability is 1 divided by the decimal price, so 1 / 1.67 is about 60%.

Fractional odds, common in the UK, show profit over stake. 13/10 means 13 of profit for every 10 staked, the same as +130 or 2.30. Whatever the format, the price and its implied probability do not change.

They can be, but they are worth less than their face value. With most bonus bets, a win pays the profit only; the stake is not returned. A $100 bonus bet at -110 that wins pays $90.91, not $190.91.

That rule changes which odds make sense. On a bet with a 50% chance at -110, the bonus is worth about 0.50 × $90.91, or $45.45. On a 25% chance at +300, it is worth 0.25 × $300, or $75. Longer odds keep more of the bonus's value.

Deposit matches and other promotions often carry playthrough rules, which require you to wager a set amount before you can withdraw. Read the terms before you accept one. A bonus that pushes you to bet more than you planned is not free.