Kelly Criterion Calculator
The Kelly Criterion is a formula for sizing bets or investments to maximize the
The Kelly Criterion is a formula for sizing bets or investments to maximize the
How to use Kelly Criterion Calculator
- Enter your estimated win probability as a percentage and the net odds you receive on a win.
- Type in your total bankroll and choose a Kelly fraction (Full, Half, or Quarter).
- Read the suggested stake percentage and dollar amount, and use a smaller fraction if you want less volatility.
About Kelly Criterion Calculator
The Kelly Criterion is a formula for sizing bets or investments to maximize the long-run growth rate of your bankroll. Enter your estimated win probability, the net odds you receive on a win (b), and your total bankroll, and this tool returns the fraction of your bankroll to stake and the dollar amount that corresponds to it. The core formula is f* = (b·p − q) / b, where p is the win probability, q is 1 − p, and b is the profit per unit risked.
The calculator also shows your edge per dollar staked (p·b − q) and lets you apply a fractional-Kelly multiplier. Full Kelly maximizes growth but is very volatile, so many bettors and investors use Half or Quarter Kelly to reduce drawdowns while keeping most of the growth benefit. If your inputs describe a bet with no positive edge, the tool tells you not to bet, because the math recommends a zero stake.
Everything runs privately in your browser with no network calls, uploads, or sign-up. The output is only as good as your inputs: Kelly assumes you know the true win probability and odds, and real-world probabilities are rarely known exactly. Overestimating your edge leads to over-betting, which is why the fractional options exist. This tool is for education and planning, not financial or gambling advice.
Frequently asked questions
- What is the Kelly Criterion formula?
- For a bet that pays net odds b on a win with win probability p (and loss probability q = 1 − p), the optimal fraction of your bankroll to stake is f* = (b·p − q) / b, which simplifies to p − q/b. This tool computes that fraction and multiplies it by your bankroll to give a dollar stake.
- What should I enter for 'net odds on a win (b)'?
- Enter the profit you make per $1 risked if you win. Even money is 1, 3-to-1 is 3, and decimal odds of 2.50 mean b = 1.50 (subtract the 1 you get back). For investing, use your average win divided by your average loss as the win/loss ratio.
- Why should I use Half or Quarter Kelly?
- Full Kelly gives the highest long-run growth but produces large swings and deep drawdowns. Because you can rarely estimate your true win probability perfectly, betting full Kelly on an overestimated edge causes over-betting and ruin risk. Half or Quarter Kelly keeps most of the growth with far less volatility.
- Why does it say 'do not bet'?
- If the win probability and odds you entered produce a negative or zero edge, the Kelly fraction is zero or negative, meaning there is no wager that grows your bankroll over time. The tool then recommends staking nothing. Raise the win probability or the payout odds to see a positive stake.
- Is my data private?
- Yes. The calculator runs entirely in your browser using JavaScript. Nothing you type is uploaded, stored, or sent anywhere, and no sign-up is required.
- Is this financial or gambling advice?
- No. This is an educational calculator that applies a mathematical formula to the numbers you provide. It cannot know your true probabilities and does not account for taxes, fees, correlation between bets, or bet limits. Use it for planning only.