Tools
Odds and probability calculators
Tools for the arithmetic behind market analysis: odds conversion, vig removal, expected value and parlay pricing. Everything computes in your browser — no input leaves the page.
- ToolOdds converterConvert American odds to decimal odds and to the probability the price implies before the bookmaker's margin is removed.
- ToolNo-vig calculatorRemove the margin from a two-way market so both sides sum to 100%, giving the probability estimate implied by the price itself.
- ToolExpected value calculatorSize the expected value of a price given your own probability estimate, and see the fair price that estimate implies.
- ToolParlay calculatorCombine independent legs into a fair combined price and see how each leg's margin compounds across the ticket.
Converter
Odds → implied probability
American odds to decimal, fractional-equivalent payout, and the probability the price implies before margin is removed.
Negative for favourites, e.g. -145.
- Implied probability
- 59.2%
- Decimal odds
- 1.690
- Payout on 100
- $168.97
- Break-even win rate
- 59.2%
No-vig
Remove the margin
Normalising both sides to sum to 100% gives the book's actual probability estimate — the number worth comparing against an exchange.
- Market hold
- 3.63%
- Booked total
- 103.63%
- Fair A
- 57.1% · -133
- Fair B
- 42.9% · +133
Expected value
Edge and EV
EV is only as good as your probability estimate. Treat the output as a sensitivity check on that estimate, not a forecast.
- Expected value
- +$8.00
- Edge vs. price
- 3.56%
- Price implies
- 44.4%
- Fair price at estimate
- +108
Parlay
Correlated-free parlay price
Multiplying independent legs compounds each leg's margin. The gap between the fair price and the offered price is where parlay hold lives.
- Combined decimal
- 7.258
- Combined American
- +626
- Implied probability
- 13.8%
- Product of legs
- 13.8%