Kelly Calculator

Estimate Kelly sizing from edge assumptions.

Inputs

Enter win rate and average profit / loss ratio.

Static local calculator

Enter your assumptions, then calculate a sizing range.

Sizing view

Read the full Kelly fraction first, then compare the calmer bands.

Awaiting inputs

Waiting for a valid edge

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A positive Kelly fraction appears when the assumed edge turns positive.

Quarter Kelly

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Most conservative reference for users who want more variance buffer.

Half Kelly

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Often used when the edge estimate is noisy or confidence is moderate.

Full Kelly

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Theoretical maximum growth fraction under the Kelly assumptions.

Edge: -- Loss rate: -- Odds multiple: --

Risk temperature

Sizing spectrum

The marker stays near calm or pushes toward assertive sizing depending on the Kelly fraction.

No sizing signal yet

Waiting for a scenario

What the calculator assumes

This tool expects two inputs: how often you win and how large the average winner is versus the average loser. It returns full, half, and quarter Kelly references. It does not estimate your edge for you, and it does not replace account-level risk limits.

Examples: compare a 55% setup at 1.8R, sanity-check a discretionary trade plan, or explain fractional Kelly sizing to a teammate.

FAQ: This calculator runs locally and does not forecast win rate for you. Use it as a sizing reference alongside account-level risk limits and drawdown rules.

Quick guide

Use cases, answers, and nearby tools

Compact below-tool notes that help first-run users and repeated visitors move faster without changing the main interface.

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How to use

Run a clean first pass

  1. Enter win probability and average profit / loss ratio.
  2. Calculate the edge and compare quarter, half, and full Kelly sizing bands.
  3. Use the spectrum and result notes to sanity-check how aggressive the fraction feels.

Examples

Real jobs this page helps with

  • Trade plan sizingCompare how a 55 percent setup at 1.8R changes across quarter, half, and full Kelly references.
  • Risk discussionShow a teammate why fractional Kelly is often calmer than using the theoretical maximum size.

FAQ

What people usually want to know

Does it estimate win rate for me?
No. You provide the edge assumptions, and the page returns sizing references from those inputs.
Should I always use full Kelly?
Not necessarily. Many users treat half or quarter Kelly as a calmer reference when edge estimates are noisy.
Is any market data required?
No. This is a static local calculator driven entirely by your inputs.