LAST NIGHT · MLBD. Swanson (CHC): 3 H · 3 HR · 8 RBI in a win over SD — Standout Index 98
LAST NIGHT · MLBM. Conforto (CHC): 3 H · 2 HR · 4 RBI in a win over SD — Standout Index 93
TRANSACTION · MLBBraves: Agreed to terms with OF Luis Consoro on a minor league contract (Jul 1)
LAST NIGHT · MLBT. Bradley (MIN): 5.0 IP · 11 K · 1 ER in a win over HOU
LAST NIGHT · MLBT. Melton (DET): 6.1 IP · 7 K in a win over NYY
TRANSACTION · MLBRoyals: Placed RHP Connor Seabold on the 15-day IL (Jul 1)
TRANSACTION · MLBPirates: Agreed to terms with SS Ryan McCarty on a minor league contract (Jul 1)
TRANSACTION · NBAWizards: Re-signed F Jamir Watkins to a two-way contract (Jul 1)
TRANSACTION · NBATrail Blazers: Signed C Branden Carlson to a contract (Jul 1)
TRANSACTION · NBAMagic: Signed F Jonathan Isaac and C Nikola Vucevic to contracts (Jul 1)
TONIGHT · WNBAATL @ WSH, 7/2 - 7:30 PM EDT — ATL -7.5
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Free tool

Kelly
Calculator

Enter a bankroll, a price, and your estimated win probability. We show the full, half, and quarter Kelly stakes, plus the limits of the formula.

Questions, answered

What does the Kelly calculator do?+

It applies the Kelly formula to a bankroll, a price, and the probability you enter. It does not verify that your probability is right.

Should I use full Kelly?+

Full Kelly is aggressive and can swing hard when an estimate is wrong. Fractional Kelly or flat stakes are usually calmer choices.

When should I avoid Kelly staking?+

Avoid it when your probability is a guess, stale, copied from a screen, or driven by emotion. Bad inputs make bad stake sizes.

Full Kelly
$83.33
8.33%
Half Kelly
$41.67
4.17%
Quarter Kelly
$20.83
2.08%
Break-even
40.0%
+5.0pp vs input

At +150, the listed price breaks even at 40.0%. The formula uses your entered probability; it does not verify that number. 21+ · Bet responsibly

When NOT to Kelly

  • Kelly assumes you KNOW your edge. This calculator does not prove one exists.
  • Garbage-in-garbage-out: a bad probability estimate makes the stake output bad.
  • Overbetting a misjudged edge ruins bankrolls faster than flat staking.
  • Most people should use fractional Kelly or flat stakes.

More like this — daily graded slate + new free tools

How it works

  • American odds convert to decimal odds. The break-even probability is 1 ÷ decimal odds.
  • Kelly uses your entered probability against that price to size a bankroll fraction.
  • The calculator shows full Kelly and smaller fractions. It is a formula, not a recommendation.