Tools
Betting calculators
The math, made hands-on. Change a number and watch it update — the same conversions and edge calculations our own research runs on. Bookmark this; you'll come back to it.
Odds Converter
American → decimal → implied win %. Read every line as a probability.
Decimal
1.67
Implied win %
60.0%
Payout / $100
$167
stake back + profit
At -150, the book prices this to hit about 60.0% of the time — that's your break-even. Beat that number and you're +EV.
Expected Value (EV) Calculator
Is a bet +EV? Compare your win % to the price's break-even.
EV %
+14.4%
EV on $100
+$14.40
Break-even
45.5%
win % to not lose
You need 45.5% to break even and think it hits 52% — that's a positive edge. Over 1,000 bets like this you'd gain about $14400.
No-Vig / Hold Calculator
Strip the juice from a two-way market to find the fair price.
Book hold
4.7%
the vig
Fair A
-104
51.1%
Fair B
+104
48.9%
The two prices imply 104.7% of probability — anything over 100% is the book's 4.7% hold. Strip it out and the fair line is -104 / +104. Beating the fair price is the edge.
Parlay Calculator
Combined odds, payout, and the true hit-probability a parlay needs.
Combined odds
+811
Payout
$182.23
+$162.23 profit
Needs to hit
11.0%
true probability
3 legs pays +811 — exciting — but every leg has to land, so the parlay only cashes about 11.0% of the time at these prices. Fun in small doses; the math is why the house loves them.
Kelly / Bankroll Sizer
How much to stake — sized to your edge, not your gut.
Suggested stake
$20.91
% of bankroll
2.1%
Your edge
+9.2%
Quarter-Kelly is the sane default — it captures most of the growth with a fraction of the swings. If your win % is a guess (it usually is), size down, not up.
Want the concepts behind the math? Start with How Odds Work, What +EV Means, and The Vig.
Educational tools, not betting advice. Estimates only — your "true win %" is a judgment call, so treat outputs as a guide, not a guarantee. 21+. Play responsibly.