Bet math, made plain.
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General Bet Calculator
e.g. +150 or -200
| American | Decimal | Fractional |
|---|---|---|
| — | — | — |
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Learn the basics
How are odds calculated?
Odds describe the payout for a winning bet. There are three common formats:
- American (used by US sportsbooks). A positive number like +150 is the profit on a $100 stake. A negative number like -200 is the stake needed to profit $100.
- Decimal (used in Europe, Australia, Canada). The number is your total return per $1 staked. 2.50 means a $1 bet pays back $2.50 total.
- Fractional (traditional UK format). 3/2 means a $2 bet returns $3 in profit, plus your $2 stake back.
All three formats describe the same thing — different ways of writing the same payout.
What is implied probability?
Implied probability is what the odds suggest the chance of winning is, expressed as a percentage. It comes from a simple formula:
implied probability = 1 / decimal odds × 100
So decimal odds of 2.00 imply a 50% chance. Decimal odds of 4.00 imply a 25% chance. If you think the true chance is higher than the implied probability, you've found value — and that's the foundation of expected-value (EV) betting.
Spreads and totals (over/under)
Point spreads and totals are sold at standard juice — most often -110 in American odds on each side. That's decimal 1.91, an implied probability of about 52.4%. The 2.4% extra above 50% is the sportsbook's vig.
Plug -110 into the calculator above to see the payout on a standard spread or total bet at any stake.