Kelly Criterion Guide

Calculates Full, Half and Quarter Kelly from bankroll, odds and estimated probability. This guide explains what to enter, the calculation logic, a worked example and how to read the result.

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1Open Kelly Criterion and start from the pre-filled example or your own data.

2Enter the requested odds, stake and any additional parameters.

3Run the calculation and check the main output first.

4Compare the detailed values or scenarios before changing one input at a time.

⌨️ What to enter

What to enter

Bankroll1000

Odds2.00

Estimated probability %55

CurrencyEUR

👀 Example

Try it like this

With a €1,000 bankroll, odds 2.00 and a 55% estimate, Full Kelly is 10% = €100; Half Kelly is €50.

💡 What it means

Read the result

The result shows the mathematical output of Kelly Criterion using the values you entered. Read the headline value first, then use the breakdown to understand how stake, odds and scenarios contribute to it.

🧠 Formula / logic

How it works

f* = (b×p − q) / b, where b = odds−1 and q = 1−p

💡 This is a mathematical output based on the values you enter. It is not a prediction and does not guarantee a future result.

⚠️ Common mistakes

Entering odds, percentages or stake in the wrong field.

Treating the output of Kelly Criterion as a prediction instead of a calculation based on the inputs.

❓ FAQ

Do I need to know the formula for Kelly Criterion?

No. The formula is shown for transparency; the calculator performs the calculation from the entered values.

Does the result tell me what to bet?

No. It is a mathematical result, not a betting recommendation.

Can I change the example values?

Yes. Start with the example, then change one value at a time to see how the result changes.