The math behind your bet slip
Bet Calculator
Calculate payouts for any odds format — American, decimal or fractional.
All calculators
A little clarity for every kind of slip.
Parlay
Combine odds across multiple picks.
Odds Converter
Same odds. Three ways to read them.
Implied Probability
See the percentage — and the margin — behind the price.
Free Bet
Stake-not-returned payouts and lay matching.
Each-Way
Separate the win and place returns.
Round Robin
Break down your bet combinations.
Hedge
Compare both sides of a position.
No-Vig
Remove the margin from the odds.
Transparent math
How the math works
Every odds format describes the same thing: how much you get back for each unit you stake. We convert everything to decimal odds first, then multiply.
Read our methodology →American −A → decimal = 1 + 100 ÷ A
Fractional n/d → decimal = 1 + n ÷ d
Payout = stake × decimal · Profit = payout − stake
Implied probability = 1 ÷ decimal
Example: $100 at −110
- Decimal odds = 1 + 100 ÷ 110 = 1.91 (exactly 21/11)
- Payout = 100 × 21/11 = $190.91
- Profit = payout − stake = $90.91
- Implied probability = 11/21 = 52.38%
FAQ
Frequently asked questions
What does −110 mean?
A minus sign shows how much you need to stake to win 100. At −110 you stake 110 to win 100, so a $100 bet wins $90.91 and returns $190.91 in total. The implied probability is 52.38%.
What does +150 mean?
A plus sign shows how much a 100 stake wins. At +150, a $100 bet wins $150.00 and returns $250.00. That is 2.50 in decimal odds and 3/2 in fractional odds.
Does the payout include my stake?
Yes. “Total payout” is your stake plus your profit. “To win” is the profit only. For example £10 at 5/2 wins £25.00 and pays out £35.00.
Why might my bookmaker show a slightly different number?
slipmath calculates with exact fractions and rounds money to the nearest cent at the end. Some bookmakers round payouts down, or apply maximum-payout limits, so their figure can differ by a cent or more.