Bet size calculator
How much of your betting money to bet when a price is good. Normal is the default.
Free, no account needed. The link keeps your numbers, so you can share them.
Your bet
Example numbers. Type your own.Odds format
Your fair chance. For example, from a site known for accurate prices (a sharp site, like Pinnacle), with its cut taken out.
The money you keep for betting only.
Bet size
Each bets a share of the full Kelly amount: Careful = 0.1, Normal = 0.25, Bold = 0.5. Normal is the default.
WynFynd's default cap is 20%.
Result
Normal bet
$11.36
That is 1.14% of your betting money.
- Full amount (full Kelly)For reference. Bet size bets a share of it.
- $45.45 · 4.55%
- Value
- +5.00%
- You win if it wins
- +$12.50
- Average profit on this betOver many bets like it
- +$0.57
How it works
- Type your fair chance of winning, the odds you can bet and your betting money.
- Kelly works out the share of your betting money to bet.
- That share grows your money fastest over the long run, if your chance is right.
- Pick a bet size. Each one bets a share of that full amount, for smaller swings.
- Normal, the default, bets a quarter of it. Careful bets less, Bold bets half.
- The cap stops any one bet going over 20% of your betting money, unless you change it.
b = decimal odds - 1f = (b x p - (1 - p)) / bAmount = f x bet size x betting moneyCareful = 0.1, Normal = 0.25, Bold = 0.5Amount is at most cap x betting moneyExample
50% at 2.10, $1,000 to bet
- b = 1.10. f = (1.10 x 0.50 - 0.50) / 1.10 = 4.55%.
- Full amount: $45.45. Bold: $22.73. Normal: $11.36. Careful: $4.55.
- The value is 5.00%. A Normal bet makes about $0.57 on average.
These are the numbers already in the calculator above.
Questions
What is the Kelly criterion?
A formula for how much of your betting money to bet when a price is good. It grows your money fastest over the long run, if your chance of winning is right.
Why not bet the full amount?
Your chance is only an estimate. If it is a little too high, the full amount bets too much. It also swings hard. Each bet size bets a share of it, so your money grows a little slower with much smaller swings. Normal, a quarter, is the default.
What if it says $0?
Then the bet has no value at those odds: the price pays less than your chance says it should. The answer is not to bet.
Where does my chance come from?
The best source is a site known for accurate prices (a sharp site, like Pinnacle). Take its cut out of its price. The fair price calculator and the value bet calculator do that for you.
Should I use this for both-sides bets?
No. A both-sides bet is split so every result pays back the same, and the both-sides calculator works that out. Bet size is for one-sided bets with value.
Learn the idea
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