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Kelly Criterion
Calculator.
Kelly Criterion Calculator: How much of my bankroll should I stake on a bet I believe has an edge? Enter four figures and this page returns stake this bet deserves, with every line of the arithmetic printed rather than hidden. The worked example below answers 41.82 for the figures it states. Free to embed. Checked 2026-08-23.
Run it on your numbers41.82
01Run it on
Run it on
your numbers.
The fields open holding the worked example below, and the answer changes as you change them. Every line of the arithmetic is printed under the result, and the formula under that — so the answer can be checked rather than trusted.
Stake this bet deserves41.82The arithmetic,
The arithmetic,
line by line.
| Step | Value |
|---|---|
| What one unit wins — decimal odds − 1 | 1.1000 |
| Expected value per unit staked at 52.00% | 0.0920 |
| Kelly fraction f* | 8.36% |
| Applied at half Kelly | 4.18% |
| Stake | 41.82 |
b = decimal odds − 1 (what one unit wins) p = your probability ÷ 100 q = 1 − p f* = (b × p − q) ÷ b (Kelly, 1956) stake = bankroll × f* × fraction, and 0 whenever f* ≤ 0
02The worked example,
The worked example,
in plain HTML.
| Input | Value | What it is |
|---|---|---|
| Bankroll | 1000 | The whole amount you are betting with, not the balance in front of you today. |
| Decimal odds offered | 2.10 | The price you can actually get. Use the odds converter if the book quotes fractions or American prices. |
| Your estimate of the true chance | 52% | Yours, and the only input here that is not a fact. Kelly amplifies an over-estimate faster than it rewards a correct one. |
| Fraction of Kelly | Half Kelly | Full Kelly is the growth-optimal stake and is far more volatile than most people expect. Fractional Kelly gives up a little growth for a much smoother ride. |
| Stake this bet deserves | 41.82 | Computed by the same function the calculator above runs. The build refuses to publish this page if the two disagree. |
At 2.10 the book is pricing the outcome at 47.62%. Believing it is really 52% is an edge of 0.092 per unit staked, and full Kelly turns that into 8.36% of the bankroll — 83.64 out of 1000, which is a much larger bet than the edge feels like. Half Kelly stakes 41.82. Enter any casino game's true probability against its true price and the same formula returns zero, because the edge is on the other side of the table.
WHAT THIS CANNOT TELL YOUWhere the answer
Where the answer
stops being one.
Every calculator on this site ends here, because the number at the top is only as good as what it leaves out — and what it leaves out is never nothing.
| Limit | What it means |
|---|---|
| What this cannot see | Kelly is only as good as the probability you typed, and that is an estimate rather than an observation. Over-estimating your edge does not merely shrink the return: it can make a positive-expectation strategy lose, because the formula stakes more the more confident you are. Full Kelly is growth-optimal and brutally volatile — drawdowns of half the bankroll are ordinary — which is why fractional Kelly exists. None of this applies to a casino game, where the edge is negative by construction and the growth-optimal stake is zero. This is arithmetic, not betting advice. |
| What it is not | Arithmetic, not advice. Nothing on this page recommends gambling, gambling more, or taking any particular bet, and no calculator turns a negative expectation into a positive one. |
03Put this on
Put this on
your own site.
Free, no account, no charge and no script of ours on your page. The snippet loads the calculator on its own in an inert frame, and keeps an attribution link outside it in your markup.
05Questions about
Questions about
this calculator.
How much of my bankroll should I stake on a bet I believe has an edge?
At 2.10 the book is pricing the outcome at 47.62%. Believing it is really 52% is an edge of 0.092 per unit staked, and full Kelly turns that into 8.36% of the bankroll — 83.64 out of 1000, which is a much larger bet than the edge feels like. Half Kelly stakes 41.82. Enter any casino game's true probability against its true price and the same formula returns zero, because the edge is on the other side of the table.
What can the kelly criterion calculator not tell me?
Kelly is only as good as the probability you typed, and that is an estimate rather than an observation. Over-estimating your edge does not merely shrink the return: it can make a positive-expectation strategy lose, because the formula stakes more the more confident you are. Full Kelly is growth-optimal and brutally volatile — drawdowns of half the bankroll are ordinary — which is why fractional Kelly exists. None of this applies to a casino game, where the edge is negative by construction and the growth-optimal stake is zero. This is arithmetic, not betting advice.
Is the kelly criterion calculator free to use and embed?
Yes. There is no account, no sign-up and no charge, the page works with JavaScript switched off, and the embed snippet on this page may be pasted into any site. The only thing asked in return is that the attribution link outside the frame is left in place.
Where this arithmetic comes from, and what it is worth.
The formula is printed in full on this page so it can be checked rather than taken. Solaspins asserts no figure of its own here: every number is either one you typed or one derived from it, and the worked example is generated by the same function the form runs. Last checked 2026-08-23. This is arithmetic — not financial, legal or gambling advice.