Odds Calculator — American, Decimal & Implied Probability

The three conversions that matter

Every price at a US sportsbook is posted in American odds, and two formulas cover everything you’ll ever need:

• Negative odds (favorite, e.g. -150): decimal = 1 + (100 / 150) = 1.667. Implied probability = 150 / (150 + 100) = 60%.
• Positive odds (underdog, e.g. +150): decimal = 1 + (150 / 100) = 2.50. Implied probability = 100 / (150 + 100) = 40%.

Payout is the same math in reverse: stake × decimal = total return, stake included. $100 at 2.50 returns $250 — that’s $150 profit plus your $100 back. Memorize the pattern and you can price any bet in your head in about five seconds: negatives divide into 100, positives divide by 100.

Why decimal at all? Because American odds don’t multiply. The moment you stack legs into a parlay or compare two books, decimal is the only format where the math stays clean. Convert, multiply, convert back — that was the entire workflow behind every ticket I ever priced.

American odds conversion table

The row to memorize is -110 — the standard juice on spreads and totals at every licensed US book. It implies 52.4%, which means you must win 52.4% of -110 bets just to break even. Those 2.4 points above a coin flip are the sportsbook’s entire business model. Every half-point of juice you shave — betting -105 instead of -110 — drops your break-even to 51.2% and is worth real money over a season.

Reading the vig: hold percentage by market

Add the implied probabilities of both sides of a market. Anything over 100% is the book’s hold — the tax you pay to play. Here’s what typical 2026 markets actually charge:

That futures number is why I almost never tie money up for six months: when 32 teams’ implied probabilities sum to 135%, you’re paying a 35% tax before a snap is played. Lower hold = better book. It’s the single most honest way to compare operators.

Worked examples

Why implied probability is the only number that counts

Odds are just a price tag. Implied probability is what the price tag says. Your whole job as a bettor is comparing the book’s number to your own estimate: bet when yours is higher, walk away when it isn’t. That’s it — everything else, trends and touts included, is noise dressed up as signal.

One warning from the desk: implied probabilities multiply down a parlay, and books round payouts in their favor. A 3-leg ticket of -110 legs carries true odds of +596 but the compounded juice means the posted payout understates the risk you’re taking — the leg-by-leg math is in the parlay payout calculator. New to the vocabulary? Start with how to bet on sports and come back.

FAQ — odds conversion questions

What does +200 mean in betting?

+200 means a $100 bet wins $200 profit ($300 total back). In decimal that’s 3.00, and it implies a 33.3% chance of winning. Any positive number reads the same way: the figure is the profit on a $100 stake.

What does -110 mean?

You risk $110 to win $100 — it’s the standard price on spread and total bets. The extra $10 is the juice. At -110 you need a 52.4% win rate to break even over time.

How do I convert odds to percentage without a calculator?

For favorites, divide the odds by (odds + 100): -150 → 150/250 = 60%. For underdogs, 100 / (odds + 100): +150 → 100/250 = 40%. Two moves, five seconds, works on any line.

Is a higher implied probability always a better bet?

No — it just means the outcome is more likely, not that the price is fair. A -500 favorite wins 83% of the time and can still be a terrible bet if the true chance is 78%. Value lives in the gap between the book’s number and yours.

Why do both sides of a market add up to more than 100%?

That surplus is the vig — the bookmaker’s margin. A fair market sums to exactly 100%. The gap over 100% is what you pay for the right to bet, and shopping for lower-hold markets is the easiest edge a recreational bettor can grab.